The CBB

Italian
Mi hai aiutato a portare a spasso il (mio) cane.
/mj‿ai̯ aju'taːto a por'taːre a 'spasso il mio̯ kaːne/
mi hai aiut-ato a portare a spasso il mi-o cane
1SG.DAT have.2SG help-PART.PASS to take to walk DEF.MS my-MS dog

I glossed "portare a spasso" quite literally, but "spasso" used outside this sentence would mean "fun". "Portare a spasso" is some sort of causative version of "andare a spasso", which means "to go for a walk".
Note that "mio" is redundant. It's quite clear that you're talking about your dog, so you can leave it out (and it would be more natural to do so).

Hecathver/Häħadhvar
Daħi mes goniam tiać strollot merg zubieħeg.
/'daki mes go'njam tjats 'strɔllot mεrg zu'bjekeg/
daħi mes goni-am tiać stroll-ot mer-g zubieħ-eg
2SG.ERG 1SG.ACC help-PAST.2SG to walk-INF.COM my-COM dog-COM

"Tiać" is more of a general-purpose particle used with some verbs than an actual preposition meaning "to". Most of the times, actually, it comes out as "from" in the English translation.

Old Laikan

Sälpəttūma myam śuno ātṣon.
[sæl.pət.tu:.ma mæm ɕu.no ɑ:.ts̺on]
sälp-ət=tū=ma myam śun-o āś-ton
help-2.SG.PRF=2.SG.NOM=1.SG.ACC 1.SG.GEN dog-ACC.SG lead-INF
You helped me walk my dog.

Edit: updated

Deyryck

daga isèlyoa tyatapa'
dog 1PS-walk 2PS-help-PAST-GOAL:none
You helped me walk my dog.

K'anerhtówhí

Imrhemúrakef weréúk wishéninwhírh.
/ɪm.r̥ɛ.mu.rɑk.ɛf wɛ.rœ.uk wɪ.sʰœn.ɪn.ʍʏr̥/
Im-rhemú-rak-ef weré-úk wishén-in-whí-rh.
1SG.OBJ-help-NPST-2SG stroll-ALL dog-1SG-H.GEN-NH.GEN
You helped me walk my dog.

Notes:
-In K'anerhtówhí, it is impossible to have two conjugated verbs in a single clause; nominalisation is prevalent. "You helped me walk my dog" is literally "You helped me with the walking of my dog".

-The two genitive suffixes are used in this sentence. The first one, the non-human genitive refers to the dog's walking (weré wishénrh, "the dog's stroll"). The second genitive, the human genitive, is used to show possession of the dog (wishéniwhí, "my dog").

-While in English, you help with something, in K'anerhtówhí you help towards a goal, hence the allative case.

-Dogs aren't native to Rajnlokem. The K'anerhtówhí have only ever been exposed to wolves, which they sometimes breed to help them hunt, or for meat. Some rich families can however afford to keep wolves as pets. They would call such an animal wishén, from hén, "wolf", and wis, "to cherish, look after". Dogs are really just wolves we cherish, after all.

Project Tri 3
Natarim bat, bagalim klifi.
natar-im bat bagal-im klifi
help\PST.ACT-2SG 1SG, accompany\ACT.PST-2SG bark\A.NMLZ
You helped me walk my dog.

I decided you don't walk a dog or walk with a dog in this conlang. This looks like a weird idiosyncracy to me. So I decided to kill two birds with one stone and use 'accompany' as the verb in this expression. Now I can derive a relational noun meaning 'with' from it. Yay
Also a dog is a 'barker', but this might just be a back-formation.

Symiric

Tásák subul rúinál kiranál rúsud.
[ˈtaːsaːk ˈsubul ˈruːi̯naːl ˈkirɑnaːl ˈruːsud]
help-2SG.PST saunter-INF 1SG-POSS.COM dog-COM 1SG-DAT
"You helped me walk my dog."

Ngolu / Iliaqu

Ti aio ua jo tuiuzu na jes oko gune.
PRF help NOM.2S.ACS ACC.C walk(TR) NOM.1S.ACS ACC.3S.DEF.ACS dog VB-GEN.1S.ACS
You helped me walk my dog.
(Literally more or less: You helped that I walk my dog.)

---

Probably more natural to incorporate dog into the verb phrase in that clause:

Ti aio ua jo tuiuzu oko na.
PRF help NOM.2S.ACS ACC.C walk(TR) dog NOM.1S.ACS
You helped me walk my dog.
(Literally more or less: You helped that I dog-walk.)

Z̧uǯ

Ḑun z̧órł msérł jon žǯúlmlsn.
2 help-PST CAUS-walk-PST 1 dog-1
You helped me walk my dog

Asta

yurenyəsə mənə‘rəre‘iyəx mənasən
yur-enyəx-yə mə-n-ə‘re<ər>-‘ə-yəx mə-nasən
2>1-help-PRF 1-IIs-wander<CAUS>-NOM-ADV 1s-dog
You helped me walk my dog

Īsmay

Ma dīttobavādh (dham) bis åma.
"You helped me walk my dog."
Literally: you helped me make my dog go back-and-forth.

Basque

Nire txakurra ateratzen lagundu didazu.
/niɾe t͡ʃakura ateɾat͡s̻en lagundu didas̻u/
ni-re txakurr=a atera-tzen lagun-du d-i-Ø-da-zu-Ø
1SG-GEN dog=ART.ABS.SG take_out-PRESP help-PP 3.ABS\PRS-AUX.DITR-SG.ABS-1SG.DAT-2SG.ERG-PRS
You helped me walk my dog.

"Me" here is an indirect object, at least for speakers in the Southern Basque Country.

Tsaqʼma

Qasautʼum ûthkhûnhrapanawin chamgur.
[qɒˈsɑwtʼʊm uːθxuːŋrɑpɒˈnɑwɪn ˈtʃæmɰʊr̥]
qa-s-autʼ-um-Ø ûthkh-ûnh-ra-panau-in chamgur-Ø
2SG>1SG-help-PRF-N.FUT stroll-CAUS-ABS-SUPERL-3SG.AN.POSS dog-ABS
'You've helped me take the dog on a walk.'

GrandPiano wrote: ↑08 Feb 2020 02:31 Basque

didazu
d-i-Ø-da-zu-Ø
3.ABS\PRS-AUX.DITR-SG.ABS-1SG.DAT-2SG.ERG-PRS

Gently remind me that, no matter how interesting Basque is, I will never, ever, attempt to learn it

Yorkish
Tha helpt me at ganne out mi t'hund.
/θə çɛl(p)t mə (ə) kan uːt mɪ‿t.hʊnt/
2SG help-PST 1SG.OBL INF go out with DEF=dog
You helped me walk the dog.

Wai zi be zyu nai zyeu mbingui zongwo.
wa=i zi be zyu na=i zye-u mbi-ngu=i zo-ngwo
2S=COP PST helpA GEN.SR 1S=COP cause-SIT animal-huntA=COP locomoteA-leg
You helped me walk the dog.
(Literally: "You helped that I make that the dog walks.")

Naguil

Ainavil elgei vidhen eonugun lai.
/aɪ̯'naːvil ɛl'gɛːi 'viːðɛn ɛɔ'nuːgun 'laːi/
Ai-nav-il el-g-ei vidh-en eo-nug-un lai.
2SG-help.free-PST 1SG-who-ACC walk-INF 1SG-dog-TMP together.
You helped me (to) walk with my dog (together).