what is the difference between "fell" and "fall" while they are both in present simple tense? (or to fell and to fall)
When I want to say on something that it felled, but in the present simple tense, can use both words? (fell and fall)?
When used in the present tense, "to fell" has a very different meaning from "to fall":
to cut down (a tree)
to beat or knock down (someone or something)
The past tense of "fell" is "felled". For example:
Thor felled his enemies with one mighty blow of his hammer.
It isn't an archaic word, but it can have a mythical or literary feel when used, like something out of stories, legends, or comic books. You should only use it if you fully understand its nuance. Otherwise you would say "cut down", "knocked over", "pushed off", or any of various other actions that would cause something to fall.