There really isn't much to fix on a derailleur cage. The guide and tension pulleys can be replaced, screws can be tightened, but that's about it. Straightening a bent cage is possible, but it's...
There's a high limit screw, a low-limit screw, an angle adjustment (AKA b-screw) screw, a barrel adjuster on the casing for the shifter cable and a clamp screw for the cable on the derailer.If it's...