Is it good to do strenght exercises one day before competition? What do you think?
It depends what the competition is and what your strength exercises are!
Anything that results in DOMS (delayed onset muscle stiffness) is probably a bad idea. But if strength is a part of your usual routine, I'm sure that light exercises could be great to help you prepare. Like most of these things, I imagine it's a pretty personal situation to be tried out and tested.