Samsung s2 freezing / restarts itself and can't update any app

[AC Question]

My phone restarts even if I don't tell it to. My phone is samsung galaxy s2 and I reset it because it was freezing and restarting itself many many times. After the reset I did all the things I had to do (gmail google name etc.) after that I saw that all the apps weren't updated. I went to google play store but it wasn't updated as well ( google play store ). After that I tried just to update youtube and it gave me the error 491. I searched about it did what it said but nothing happened. After seeing that I downloaded aptoide so I can update the apps. While trying to update them again the phone again freezes or restarts for no reason. I did update youtube and google play store but I can't install any app on it , or it freezes / restarts itself. You might ask : But you have aptoide and you can download and update any app. Why don't you do that? I went on the updated youtube and it said he needed google play service updated so I can run updated youtube. And when I press "ok" it opens google play store at the app google play service and it freezes or restarts itself. WHAT DO I DO????????