Upper leg bends inside lower leg I have a problem with the knee, it doesn't bend smoothly, it's just getting inside each other, please help, I was struggling with it the whole day, I managed to do the hand but the leg is a lot harder.

Thanks for your attention!

P.S. Fist time asking help :)
For this you may want to subdivide the object, then make it a softbody. When animated, the softbody will collide with itself (with the right settings), and it won't look as weird. Make sure you check the Self collision box so that it does collide with itself.