Translation:I came home and I drank milk with my mother.
While I have met learners who have difficulties pronouncing chonaic, and sometimes end up saying something that could pass for tháinig, there shouldn't be any difficulty in telling the two words apart - th doesn't shound like ch, á doesn't sound like o and ic doesn't sound like ig. Even where one of these sounds might be ambiguous, it would be unusual to get all 3 wrong. In the case of this particular exercise, it clearly starts with a th sound, not a ch sound.
Chonaic sí a buachaill le cailín eile
Chonaic mé an féinphic ar an Idirlíon
Chonaic siad an grianghraf deas inné
Chonaic sibh an bogha báistí
Chonaic siad na cnoic glasa
Tháinig siad anuas de
Tháinig mé abhaile agus d'ól mé bainne le mo mháthair
Tháinig mé ar an suíomh gréasáin