Lock the axles?

I have recently had a G 270 Bj 2002 with a safe mileage of only 70000 km Since I have little to no experience with off-road vehicles so far and am absolutely beginner with regard to Mercedes G I hope to get some helpful tips here. 1. The center and axle locks switch only very reluctantly. The light up of the red confirmation takes different lengths. The middle sometimes goes immediately, shortly afterwards, next attempt, it takes very long or several attempts are necessary Ig. rear axle as well. Front axle always lasts very long, several hundred meters driving distance, sometimes nothing happens at all, there is no feedback. 2. The doors, especially the rear door, are difficult. Out of hinges rust exits. Can one the fat or which possibility of remedy are known. Torsten Block