kite, this is very basic English.
You need to know the forms of "to be" "to have" and "to do" thoroughly.
With regular verbs, the third person singular has an S. The rest do not.
I, you, we, they cut
I, you, we, they sneeze
I, you, we, they yell
And so on.
Don't try to learn any more about tenses until you understand this backwards and forwards.
Student or Learner