Well first of all gaining muscle isn't easy. You need a routine, you need to be focused, and you need to workout properly.
You didn't explain your routine so I cant give you any tips on that, all I can tell you is that looking at your pictures you clearly gained some muscle especially in your shoulders.
Remember, if you want to gain weight you need to eat a surplus of calories. You can do what I did the first time and dirty bulk, just eat whatever and workout consistently and you'll see gains. You quit two months in but if you would've given it two more months you would have seem some real gains.
Anyways dude goodluck, most important thing is to stick with it.
You should google the PPL workout routine, amazing for beginners.