if i make a model of stair and put them in a level will my character be able to go up them just normally or will he just go through it.

Hm, it really depends on alot of things. If the stairs are to high it wont work. There is a good tutorial about this in RESCOURCES and one of the FPS tutorials. Well documented.

Good luck

You can just place a long block diagonal in the stairs (like a catwalk) and make this blick invisible.
For 3rd person games it will be unrealistic, but fot 1st person games it might be a tip.

thanks did think of that but i am doing a 3rd person. so mayeb i could just duplicate the stairs in wed put it in the exact same spot and mkae it invisible. would that be ok.