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

[cntrational]

Inglisj

Ay öndasjtanna hwa þü gasegj. Du telc Inglisj!
1sg understand-neg what 2sg PROG-say. IMP talk English
I don't understand what you're saying. Speak English!

[alynnidalar]

Tirina

Ton napresi frosa toalenahi yes. Tofisalenahi inlansi!
NEG FEM-understand what MASC-say 2SG.MASC. MASC-IMP-speak English
I don't understand what you're saying. Speak English!

[Squall]

Xioran
Min se getxiprayns non ley kwe tu se tagrayns. Tagray mow Xioran.
1SG be.PRS get_comprehension-GER NEG DEF.SG REL 2SG be.PRS speak-GER. speak-IMP.2SG PREP.manner Xioran.
I am not getting the one that you are speaking. Speak in the way of Xioran.

Não percebo o que estás a dizer. Fala Português!

I do not know if it is correct in Portugal, but it is wrong in Brazil.
It seems to mean:
I do not notice what you are about to say.

pt_br
Não entendo o que você está dizendo. Fale em Português!
NEG understand-PRS.1SG [o que => what] 2SG be.PRS.3SG say.GER. speak-IMP.3SG LOC Portuguese.

[Chagen]

Pazmat:

Mētvūtṛ acya kāqqāmvūya yina. Pazmatya matēm'!
speak-INFIN-GEN what-ACC understand-INFIN-ACC NEG.IMPERF-1S pazmat-ACC speak-DEON

Note that this literally translates to "I am not understanding what you're saying", as the implication is that I will understand later. Using the aorist (which would be translated "I don't understand...") would sound like I will never understand you as long as I live, which...rather insulting.

[All4Ɇn]

Niijerj

Eu nè comprend quis tu dirs. T'-parls Niijerj!
[ɔʏ̯ nə ɣom.rɛnd kis ty dir tarl ni.jerʒ]

[Täzari]

Lözusöteli
Besætzinæ hvå/hvad ræbit. Seknekot lözusötelil!

Aynu
Hemanta e=itak ya k=erampewtek wa. Aynu itak ani itak!

Japanese
I saw there is already a translation in Japanese but I think that it should be 日本語で話せ instead of 日本語を話せ... I'll wait for a native speaker to solve this.

Nivkh
Here I want to try to provide also a Nivkh translation. The only thing I'm not sure about is the usage of the verb "p'ur-" with the name of a language, maybe there is another more appropriate verb. I'll look up for this!

ɲi t̩'i iřt̩p'anp'arad̩ra. ɲivx p'urja!

Usually Nivkh is written using a modified Russian alphabet but I prefer to write it using the IPA alphabet. This is just for my own comfort.

[thaen]

lirlæmitul sæmulæhhæl. pálǽhkákéær Nillæhimmæ!

[thetha]

Don't do that. Just post yours.

[Jackk]

Puēnncech

àgāhē wo isūknbou. haisūk encech!
I don't understand what you're saying. Speak English!

Spoiler:

/ɑˈkaːheː wo iˈsuːkmbow ‖ hajˈsuːk enˈgeʃ/
à-gā-hē wo i-sūk-n-bou. hai-sūk encech!
1s.NOM.PRS-NEG-understand 3s.SUBD 2s.NOM.PRS-talk-IPFV-OBJ IMP-talk Encech

[Imralu]

Ngolu

Kka lumi ene zuo zoi mo vu. E ila ilia!
be.not be.understood DAT.1s.MASC NOM.C say be.what NOM.2s.ANIM | IMP speak speech
I don't understand what you're saying. Speak Ngolu.

[Thrice Xandvii]

Isλǫtaλao:
Wæ tæta lęswa kǫλę́tijǫs, isλǫtaλu lúqitæhu!
/wɑɪ̯ 'tɑɪ̯.tɑ 'lɛ̃s.wɑ kɔ̃'ɬɛ̃.ti.ʔɔ̃s | is.ɬɔ̃'tɑ.lu 'lukwi.tɑɪ̯.xu/
Wæ ta-tæ lęswa-Ø kǫλę́t-i-jǫs, isλǫtaλ-u luq-itæ-hu!
1SG 2SG-GEN language-DIR grasp-1SG.PRS-NEG, Isλǫtaλao-OBL speak-2SG.IMP-INST.DEF
I don't understand your language, speak (with) Isλǫtaλao!

(Nice to flex the imperative form now and again... Also, the accent is added because of the negation suffix, which will preserve the stress pattern of the verb form before it was added.)

[Canis]

Ahtialan
Нє· варна тєравsт ірљу кієнау, чєдукіиs ӓлаѵаі!
[nɛ vr̩nä tɛ.ˈräŭst ir.li˞ ˈkiĕ.ˌnäŭ . t͡ʃe.ˈdu.kiĭiːs ˈäĭ.ɫɑ.ˌwa.i]
no 1SG-ACT understand-INF GEN-2SG language, use-IMP Ahtialan

Polish
Nie rozumiem, co mówisz. Mów po polsku!
[ɲe rɔ.zuˈmʲem t͡sɔ ˈmuviʂ . muf pɔ‿ˈpɔl.sku]
no understand-1SG what speak-2SG . speak-IMP in_language Polish
"Po" is a preposition meaning "after", which combined with adjectives in Dative case will form a structure like "in language x".

[Xing]

Nizhmel

Cèwon ziòwu gane zhuomna sòlie. Nizhmelhak gawok!
[t͡ʂʰɛ̀ːon zʲø̀ːoː káːnɛː ʐúmnaː sɔ̀ːlʲeː nʲíʐmɛlak káːok]

Code: Select all

cè-won ziò-wu     ga-ne        zhuom-na    sòlie   Nizhmel-hak ga-wok
1-DAT  2-GEN  speak-NMLZ understand-can     NEG   Nizhmel-CASE ga-wok

I've decided that the subject shall be in the dative case when the verb takes the suffix -na (which expresses ability.)

-hak is a case that I don't know what to call yet.

[Dormouse559]

Updating Silvish:

Gzo nen entellé cuelca tu dicz. Palla li selvesc.
[ˈdʑɔ nə‿nɛntɛlˈlɛ ˈkʊ̯ɛlka ˈto ˈdetɕ | ˈpalla lɪ sɛlˈvɛsk]
1SG NEG understand[1SG] what 2SG say[2SG]. Speak-IMP.2SG DEF.OBL.M Silvish
I don't understand what you're saying. Speak Silvish.

[Ahzoh]

Vrkhazhian
Žaẏ tupašdudu ʾišak ruraž ʾitim. Wišda t-ʾAšdu Yat-Vṛḵaž!
1s-NOM ACC-speaking-NEUT.SG 2ms-GEN understand\ACT.PRES.SG NEG | JUSS-speak\ACT.PRES.SG ACC-mouth-NEUT.SG.CONST Vrkhazh-GEN.NEUT.SG
I don't understand what you are saying. Speak Vrkhazhian!

[Imralu]

Ngolu 2.0 / Iliaqu

Before contact with the outside world and other cultures, the Ngolu had no word for their own language other than ilia 'speech'. To differentiate it from other languages, it may now be known as ilia qu 'Qu speech' or iliaqu. The backformation ila qu or ilaqu means 'to speak Ngolu'.

Translated most literally:

• Kka lumi eni zuo zoi mo vu. E ilaqu!
  be.not be.understood DAT.1s.ICS NOM.C say be.what NOM.2s.ICS | be.IMP speak.Ngolu
  I don't understand what you're saying. Speak Ngolu. - Inaccessible mode

Perhaps more natural:

• Kka lumi eni xu ilia guui. Kua ilaqu!
  be.not be.understood DAT.1s.ICS NOM.3s.INAN.DEF.REL be.speech COP-GEN.2s.ICS | be.JUSS speak.Ngolu
  I don't understand your speech. Please speak Ngolu. - Inaccessible mode
  
  Kka lumi eni xu ilia guue. E ilaqu!
  be.not be.understood DAT.1s.ICS NOM.3s.INAN.DEF.REL be.speech COP-GEN.2s.ACS | be.IMP speak.Ngolu
  I don't understand your speech. Speak Ngolu. - Dominant mode
  
  Kka lumi ene xu ilia guue. E ilaqu!
  be.not be.understood DAT.1s.ACS NOM.3s.INAN.DEF.REL be.speech COP-GEN.2s.ACS | be.IMP speak.Ngolu
  I don't understand your speech. Speak Ngolu. - Accessible mode

[Runomso]

I don't understand what you're saying. Speak (Language)!

Rreyúndiru fidóyeme to ma. Rúnzi úkikume!

rreyún|di|ru fidóye|me to ma. rún|zi úkiku|me!
to understand 1SG.NEG. saying ACC. of you ACC. speak IMP. úkiku ACC.

[J_from_Holland]

Bløjhvåtterskyll

Mi unny Dykint z dänne! Blå Ænskyll!
I understand.not what.is.said.ACC your.ACC! Speak.IMP English!

Dykin (ACC Dykint) is a noun wich means something like 'what is said' (or, reading Imralu's post, 'speech').

In this sentence I used the masculine personal pronouns.
If the speaker was a woman, she'd have said: Ma unjainy Dykint z dänne! Blå Ænskyll!
If the person who isn't understood by the speaker was a woman, the speaker would have said: Mi unny Dykint z dunne! Blå Ænskyll!
And if both were a woman... yes, you'll probably understand this one.

[Nannalu]

Ttɯŋjṹol:
Ná ka ʔɯ́l yã uẽ́ẽ́c. Uã́c ttɯŋ-jṹol yĩ!
[na˦ ka ʔɯl˦ jã wẽ:c˦ | wãc˦ ʈɯŋɟũol˦ jĩ]
1.SG NEG=understand 1.POSS.SG=PL/speech. speak Ttwngjuol 2.SG

[J_from_Holland]

Ttɯŋjṹol:
Ná ka ʔɯ́ɯ́l yã uẽ́ẽ́c. Uã́c ttɯŋ-jṹol yĩ!

I'd like to see a gloss, and with all those diacritics, I'd like to see a pronunciation too.