I don't know what happend to my LCR?

I got an iPhone 4 with a broken LCR screen from my dad(What a present... :D), and he said I should bring it into a store and let it be fixed. I got it fixed in an unauthorized "apple store" in Indonesia, as the nearest Apple Store is in Singapore. He fixed it for a cheap price actually, around 50$. I took the phone happilly but then I noticed problems. Weak WiFi, Broken Sleep Button, Broken Volume Button... I decided to get a look into the phone myself, and it was just...ridiculous... There were 2 missing screws at the volume area, every screw was weak, and the battery almost fell off. And then I decided to go to complain to him, and then he fixed it again, no problems afterwards. I'm in my vacation now, and I fell my iPhone really slow onto a CARPET from around 30cm. Then the worst thing happend, the phone was stuck on the page I was on. I thought it was a software problem, but then I saw little white strpes in the corners. So I knew it was the LCR. I let it be, and then the stripes grew bigger and bigger, creating a big white circle in the middle covered with gray at the corners. The next day, my phone fell down again. Suddenly, my phone worked again! It's not perfect, the screen was changing rightness every few seconds, but at least it was working! Now, I guess the problem was weak screws, because my lock button and volume button stopped working again... Is there a guide to like strenghten every screw in the phone?

Thank you!