RPG Platformer

Ok, heres what I’m doing. I think I will be able to apply the elements I recieved from people in my other thread, but here is what im doing. I am making a sidescroller platformer. The character basically goes on a linear path, encounters enemies and uses his various weapons to attack. I want there to be two bars on the bottom, a life bar of the hero, and the life bar of the current enemy that you just attacked. I also want the hero to gather various weapons and be able to switch between them BEFORE the level begins. The things I need to know how to do is the lifebar stuff, I’m not sure how I would make the lifebar of a current enemy fill in the blank enemy lifebar. I also need to know how to do the weapon switching, and the inventory. Thank you very much to anyone who can help.