Both " いきます” and " たべます” are in present tense. ” いきます” is です/ます style of " いく” which means to go. And " たべます” is also です/ます style of " たべる” which means to eat.
” しています” is a progressive form or a present perfect tense. The present tense of "しています” is " する”. The です/ますstyle of " する" is " します”.
If my tips make you confused, I am sorry but I hope they will work well to you.