Past Simple:

утвердительный: I studied French when I was in high school.отрицательный: I didn't go to the party last night.

Present Simple:

утвердительный: She works as a nurse at the hospital.отрицательный: They don't eat meat.

Present Perfect:

утвердительный: We have finished our homework.отрицательный: They haven't seen the new movie yet.