The more you move your foreskin back and forth over the head and rim, the more it will stretch. Apply plenty of lubrication and use your fist or fingers in the usual masturbation movements to slide your foreskin constantly back down the shaft and then forwards over the head. If you ejaculate quickly, give it a rest and try again later. Do this a couple of times a day.
Yes — probably. We’re all different of course, so I can’t guarantee that will be the result for you personally. It will take some time; patience and persistence are required. Make sure you do this gently to avoid splitting or tearing of the skin.