I don't understand what you're saying. Speak English!

[ixals]

Cissian

Не разумем, чо говорiш. Говорi цiски!
/nʲe ra.zuˈmʲem t͡ʃo ɦoˈʋo.rʲiʃ | ɦoˈʋo.rʲi ˈt͡sʲis.ki/
[ɲe rä.z̪uˈmʲem t͡ʂo ɦoˈʋɔr.jiʂ | ɦoˈʋɔr.ji ˈt̪͡s̪ʲis̪.ki]
nye razum-yém, čo hovór-yiš | hovór-yi cyísk-i
NEG understand.IMP-1SG REL.ACC say.IMP-2SG | say.IMP-IMPR.2SG Cissian-SG.ACC
“I don't understand what you're saying. Speak English!”

[Reyzadren]

griuskant (without the conscript)

aesk shur ijshira ostae kigen. zhostar griuskant.
/'esk 'ʃur 'idʒʃira 'ɔste 'kigən. 'ʒɔstar 'griuskant/
1SG NEG advanced.know-V 2SG-POSS talk-N-PASS. use-V-IMP griuskant

[Pāṇini]

Nasiǝl/Cappadocian:

Ammuħ kuit zit memayǝ sakimuǝm natta. Tarcikǝtel zit Nasiǝl!
/ˈamːux kujt zit ˈmemajə ˈsakimwəm natːa. tarˈd͡ʒikətel zit ˈnasiəl!/
1SG.NOM what-ACC 2SG.NOM say-2SG.PRES understand-1SG.PRES NEG. speak-IMP 2SG.NOM Cappadocian-ACC!

[Mándinrùh]

Bwángxùd
SINGULAR YOU
Rudmíkang bwumbwum bùnkang bùnbandángman. Bwángxùdnat bwù!
Rud-mí-kang bwum~bwum bùn-kang bùn-bandáng-man. Bwángxùd-nat bwù!
2-PASS-DECL thing~PL PROX-DECL PROX-understanding-NEG. Bwángxùd-INS PRS;IMP!
I have no understanding of the things you say. Use Bwángxùd!

PLURAL YOU
Rudrudmíkang bwumbwum bùnkang bùnbandángman. Bwángxùdnat bwù!
Rud~rud-mí-kang bwum~bwum bùn-kang bùn-bandáng-man. Bwángxùd-nat bwù!
2~PL-PASS-DECL thing~PL PROX-DECL PROX-understanding-NEG. Bwángxùd-INS PRS;IMP!
I have no understanding of the things you say. Use Bwángxùd!

Ecclesiastical Atili
SINGULAR YOU
Ja-i-vasá-so et-kim-ag-zíe. Atíli kim-te-ák-so!
NEG-1-see-CLF C 2-talk-INS-thing. Atili talk-IMP-INS-CLF!
I do not see what you talk with. Talk with Atili!

PLURAL YOU
Ja-i-vasá-so et-kim-ag-zié-u. Atíli kim-te-ak-só-u!
NEG-1-see-CLF C 2-talk-INS-thing-PL. Atili talk-IMP-INS-CLF-PL!
I do not see what you talk with. Talk with Atili!

EDIT: Changed Atili based on

[marvelous]

Kemwiswi

I don't understand what you're saying. Speak Kemwiswi!
Lipêcunolrêêni otî yilräci. Yulri Kêmwḭ̂swî!
/li.pɛ.ʃu.nolˈrɛː.ni ˈo.tɪ jilˈræ.ʃi ˈjul.ri kɛˈmwɪ̃.swɪ/
lipêcun-olr-êêni ot-î y-ilr-äci. y-ulri kemwiswi
understand-NPFV.PRSNT.NR-1SG.NR DEM-ABSTR say-NPFV.PRSNT.SBJ speak-IMP Kemwiswi

[marvelous]

Tranzydjá

I don't understand what you're saying. Speak Tranzydjá!

No ikh widh essi dikhenze. Porola Tranzydjá!
[no ˈix wið ˈesːi diˈxen.ze poˈrola tran.zyˈdʒa]
no ikh-0 width ess-i dikh-enze porol-a tranzydjá
NEG understand-1SG.PRSNT.INDIC REL.INAN be-2SG.PRSNT.INDIC say-PROG speak-IMP.SG Tranzydjá

[Tuyono]

Źilaa Ruńu

maz liuk huuni naśal em ceeĺu. śalme ĺaa leng źilaa ruńu!

NEG reach.IPF.3SG 1SG.ACC VN-say.IPF of 2SG.OBL | say-2SG.IMP 3.INAN.ACC INST language.ACC NAME-OBL

"The thing you're saying is not reaching me. Say it with the language of Ruń!"

[Dormouse559]

Updating Silvish

Quite polite; for addressing a single person or a group:
Jou compran pà s' que vou dditte. Predjet silvé, s' ê vou pplé !
[ʑu.kɔ̃ˈpʁɑ̃ŋ ˈpa ske.vuˈdit.tə | pʁɛˈʑɛt siˈve sɛː.vuˈple]
1S.NOM understand NEG PRO REL-ACC 2FORM/2P say-2FORM/2P | speak-IMP.2FORM/2P silvish if 3.NOM 2FORM/2P please

Less polite; all right for addressing a friend or family member:
Jou compran pà s' que tu dit. Predja (doncha) silvé !
[ʑu.kɔ̃ˈpʁɑ̃ŋ ˈpa ske.tyˈdit | ˈpʁɛd.dʑə (ˈdɔ̃ɲ̟.ɕə) siˈve]
1S.NOM understand NEG PRO REL-ACC 2S say-2S | speak-IMP.2S (please) silvish

I don't understand what you're saying. Speak Silvish!

---

Nowadays, "if" is usually expressed with s' que (gloss: if SBRD), but the form without que has been fossilized in a few expressions, such as the one for "please", s' ê vou pplé (lit. if it pleases you).

As I noted above, the second translation is acceptable for addressing family members. When the family member is at least one generation above the speaker, it is good form to add doncha, which is a more familiar way of saying please. There isn't a particular expectation that you say please to other members of the family or to friends, except for emphasis. In other contexts where you might use the second translation, like on the internet, you could add s' ê te plé at the end, which is less formal than s' ê vou pplé, but maintains the distance of acquaintances.

[J Reggie]

Mýr

Kicìcỳtytú mipìnynagídidi. Cakàbugíbírýbímýri.

Ki-cìcỳt-ytú mi-pìnynag-í-didi. Ca-kàbug-íbí-rýbímýri.

2SG-speak-EVID 1SG-understand-but-NEG. 3SG-be.spoken-IMP-Mýr.language

I hear you speaking, but I don't understand. Speak Mýr! (Lit. Mýr must be spoken.)

[holbuzvala]

ASVOLAI
I don’t understand what you’re saying. Speak Asvolai!

Hol kibuwahasagatan tinvu toa kibuswala. Swala tasvolai!
Hol ki-bu-wahasaga-tan t-invu toa ki-bu-swala. Swala t-asvolai
1s.nom human.subj-abs.obj-UNDERSTAND-neg obj-THIS.abs 2s.nom human.subj-abs-obj-SPEAK. SPEAK.imp obj-Asvolai

N.B. The verb ‘wahasaga’ for ‘understand’ is a compound verb from waha (listen) and saga (see), and refers only to aural understanding.

[spanick]

Weddisch
Ik nê understann wet du seist! Spêk Weddisch!
/ɪk ne undəɾstanː vɛt duː zɛɪst | spek vɛdɪʃ/

[Birdlang]

Classical Birdish
Aokgniq shnyaéyh nÿokiéira. Salenng Bhëup Câh/Ôcñi’ šñaéç njiocéira. Salẽŋŋ Ƀươp̛ Ćā̃
/ɔc.ɲiʔ ʃɲaeç nji.o.cei.ra sa.lə̃ŋː ɓɯʌp˺ ʨãː/
NEG-understand say-3SG what-3SG, speak bird language.
I don’t understand what you’re saying. Speak English!

[Gluestick]

Lithuanian

Nesuprantu, ką sakai. Kalbėk lietuviškai!
NEG-understand-1s.PRS what-ACC say-2s.PRS speak-2s.IMP lithuanian-ADV

[gokupwned5]

Andalusí
Lis nefhem kilmatni. Gûl Andelusiy!
/lɪs nɛfhɛm kɪlmatnɪ guːl andɛlʊsɪj/
NEG understand.1.PRES.SG word-PLU-1.SG.POSS speak.IMP Andalusí
I don't understand your words. Speak Andalusí!

[All4Ɇn]

Ik verstah neut, wat du seggs. Tal Läpsjen an!
/ək fərˈstɑː nət vat də zɛks tɑːl ˈlɛpʃən an/
I don't understand what you're saying. Speak Lapdeutsch!

I chose to render this in a more casual, less German sounding way. More formal speech would sound closer to German.

[Dormouse559]

Once again, updating Silvish

Quite polite; for addressing a single person or a group:
Jo comprin pa s' que vou ddìtte. Prejé silvoû, s' î vou pples !
[ʒo.kɔ̃ˈpʁɛ̃ŋ ˈpa ske.vuˈdit.tə | pʁəˈʒe siˈvuː siː.vuˈplɛs]
1S.NOM understand NEG PRO REL-ACC 2FORM/2P say-2FORM/2P | speak-IMP.2FORM/2P silvish if 3.NOM 2FORM/2P please

Less polite; all right for addressing a friend or family member:
Jo comprin pa s' que tu dî. Prêje (don) silvoû !
[ʒo.kɔ̃ˈpʁɛ̃ŋ ˈpa ske.tyˈdiː | ˈpʁɛː.ʒə (ˈdɔ̃ŋ) siˈvuː]
1S.NOM understand NEG PRO REL-ACC 2S say-2S | speak-IMP.2S (please) silvish

I don't understand what you're saying. Speak Silvish!

It's been over a year, so I thought a quick update would be good. Structurally, things are still the same, for these sentences anyway. My notes from my previous version still apply, so I've spoilered them below with updated Silvish. The sound changes and orthography have changed, though, so that some words are pronounced differently, and words that are still pronounced the same are spelled a little differently.

Spoiler:

Nowadays, "if" is usually expressed with s' que (gloss: if SBRD), but the form without que has been fossilized in a few expressions, such as the one for "please", s' î vou pples (lit. if it pleases you).

As I noted above, the second translation is acceptable for addressing family members. When the family member is at least one generation above the speaker, it is good form to add don, which is a more familiar way of saying please. There isn't a particular expectation that you say please to other members of the family or to friends, except for emphasis. In other contexts where you might use the second translation, like on the internet, you could add s' î te ples at the end, which is less formal than s' î vou pples, but maintains the distance of acquaintances.

[Salmoneus]

Old Wenthish:

Ne frath ec thienha worden. Segi Uades tungon!


(I do not understand your words. Speak (pronounce, utter) Wade's tongue!

[Void]

Tsaqʼma

As sjusirtsiu tûshunhraqan. Qtsaqtûshunsau!
[ɑsːjʏˈsɪrtsɪw tuːˈʃʏŋrɑqɒn qtsɑqtuːˈʃʏnsɑw]
NEG 1SG>3SG.IN-understand speech-ABS-2SG.POSS 2SG-tsaqʼma:speak-FUT.SUBJ
"I don't understand what you're saying. Speak Tsaqʼma!"

[GrandPiano]

Basque

Ez dut ulertzen zer diozun. Euskaraz hitz egin!
/es̻ dut ulert͡s̻en s̻er di.os̻un | eus̺kaɾas̻ it͡s̻ egin/
[es̻ tut ulert͡s̻en t͡s̻er ði.os̻un | eus̺kaɾas̻ it͡s̻ eɣiɲ]
ez d-Ø-u-t uler-tzen zer-Ø d-io-zu-Ø-n | euskara=z hitz=Ø egi-n
NEG 3.ABS.PRS-SG.ABS-AUX.TR-1SG.ERG understand-PRESP what-ABS 3.ABS.PRS-say-2SG.ERG-SG.ABS-COMP | Basque=INSTR.INDF word=ABS.INDF do-PP
I don't understand what you're saying. Speak Basque!

[Parlox]

Gondolan

Mi s’foinos banna oblirinon, ri Gändölansch oblir!
/mĩ sfo̜i.nõ̜s bæ.nã o̜.bliɹ̠.i.nõ̜n ɹ̠i gɑn.do̜.lant͡ʃ o̜.bliɹ̠/
[1ST.ERG.SING NEG-understand.PRES.ACT 2ND.GEN.SING word-PROX.ABS.PLUR, COMMA Gondolan speak.PRES.ACT]
I don’t understand what you’re saying, speak Gondolan! (Lit. I not understanding your words, Gondolan speaking!)

Despite Gondolan being a pro-drop language, dropping a subject pronoun when it has an object itself is common. Oftentimes in these clauses the object is shifted to the subject position. If one were to say this more formally you could say Banör ri oblir Gändölansch.

This is also a good case of case dropping, which is a rarity in Gondolan and mostly a holdover from it's proto-language. Despite this being a rare style overall it is common in command and request clauses. Case is only ever dropped on the subject of a clause.