on mobile app there are always some bugs, on the computer everything is normal

HI guys, I have a problem. Why always my game works perfectly on PC, but when I build apk
on my androids there are always some bugs. (for example, ground is white, not black, character
disappears after few seconds).

Do I have to change something in build settings?
My game is not demanding to run, its very simple(27mb).

 

any suggestion?

 

So this is all I do when I make a game.
1. First I make a game (for example Doodle Jump replica)
2. I put the scenes in build settings, click switch platform to android
3. I changed the company name and product name and press build

This is my (default) settings https://imgur.com/a/uZS4SoC

So for example, I made three levels everything works perfectly, but on the phone character dissapear
after a few seconds.

I searched on the internet and found that Api compatibility Level can be the problem.
Also when I click build settings I get warning "
Failed getting available Android API levels. Make sure your android sdk tools version is 25 or higher and you have internet connection." (maybe that's a problem, but I think I have sdk, because Unity build my game but with some bugs)

 

The game works good in some phones but in some android there are bugs..how could I over come this issue