たべません。/ I don't eat

たべません

this can be divided into two parts.

たべ　＋　ません

"たべ" is a stem of the verb "eat". As you learned before, masu-form of this verb is "たべます" which is "たべ+ます". Masu-form is a positive sentence. And, you change "ます" into "ません" to make a negative. It is...

たべません

This means "don't eat.".

のみます

this means "I drink". And change "ます" into "ません" to create a negative...

のみません

this means "not drink.".