How to fix a white screen iphone 4s?

Hello!

I've had a problem with my iphone for a while now. I dropped it at the beginning of November but it worked fine so I didn't change the screen yet. However it started turning off at around 30% now and I'm unable to turn it back on. I usually manage after about 20 minutes but it brings me a lot of stress. The screen goes white with thin lines going from the top to the bottom. It also shows water damage marks but that disappears when I manage to switch it back on. Restarting it doesn't really help much and I just don't know what to do anymore. I can't afford a new phone and this one is on contract. I know that if I go to apple they will want a lot of money for the repair. Please help me manage this somehow!