Why is my Samsung S3 Mini turning off by itself, closing all apps with This app has stopped error?

Since last month, my Samsung S3 mini starting switching off by itself, closing all apps with stopped errors and get stuck on the Samsung Boot logo.

I initially thought the problem was the battery itself, so I ordered a new one and I tried it but all the issues above still persist. I don't know what could be causing this or what to do to fix it. I have Factory Resetted the phone 3 times to no avail, losing information in the process due to my lack of paticience.

Is my phone still fixable or am I SOL?

Hey, I would probably suggest getting a new phone - the S3 is quite old. You could spend quite a lot of money investing into the phone for it to work, but it wouldn't be worth it.