"Dad drinks beer every evening."
Translation:Baba anakunywa bia kila jioni.
I learned that ku- is always leaving in the present as Long as the word has more than one syllable. So here it should be: Baba ananywa bia kila jioni. Because ku- ny-wa has 2 syllables.
You are correct that ku- (the prefix) leaves. But ku- is not the prefix in this word. It would not be correct to say "kuanakunywa" because when conjugating the verb, we remove the infinitive prefix like you say.