That probably wasn't a good idea, as it will hinder learners who don't know that "tóg" has more than one meaning.
Duolingo lessons aren't just tests of what you already know, they're also the primary way of teaching new knowledge. If "tógann" isn't shown as "build" in exercises where that's a far more sensible translation, then the lesson is failing the student.
English has a lot of these also:
Rook - a bird; to steal
Flag - a banner; to tire;
Wake - to come out of sleep; a swath left when something has passed through water
Left - the opposite of right; something not needed
Hail - ice balls; homage to someone
Deck - a porch; a punch to the face
Granted, a lot of these English words change from noun to verb and so forth, but I imagine the Irish language has many such words with multiple meanings. Don't give up!