Blue screen of death

I've got an Iphone 5s from my friend and I used it for 20 days without any problems, One day at work wanted to call my wife and then the second I unlocked the screen my phone showed blue screen for 2 seconds and then went to apple logo. It wouldnt turn on for a while and then I started holding the home button and somehow I got it back,and at the moment I thought it was some kind of sudden problems and thought Its ok. but then same day in the evening it started doing it and it did 5 times and then turned off. And next day I wasn't able to use it at all because it was just keep rebooting with the blue screen. Then I got curious abt it and I took my tools and start digging it out. When I reach to board I noticed that phone had some kind of screen replacement or something. But one of those famous 4 screws was missing (top left),and the covering shield on the home button wire was also missing,wifi wire wasn't connected where it supposed to and the battery looked like it's been touched. So after all I got nervous and I did some fixing on my own after reading hundred of articles abt it ( like checking the screws if they were in the right spot,and put the wifi wire back) and of course not entirely but it seemed like I have done something good. So I've had my phone working for another 20 hours. I was just about to think that I've fixed it and then boom same story again. Lately its lasting longer than it used to before I put my hands in it but now I have a question. I have read many things on forums and stuff and everybody says it might be the "wrong screw trashing the logic board" thing.If it is,is it possible that I could use my phone like I described above? Or I have some other problem ? What do you guys think ?