MacBook Air not booting up properly

I’ve had a MacBook Air for almost 5 years now and never had any major problems with it. A few months ago, my charger stopped working and my father bought me a new one. Unbeknownst to him at the time, he bought a voltage higher than the battery could handle.

Everything was working fine for quite a while til around the holidays when the battery stopped holding its charge. I figured I’d just leave it plugged in since I do anyways (unless I’m traveling).

About a month ago, my computer wouldn’t boot up properly the odd time, in which case I’d have to run a quick hardware test just so it would. I found this happening more frequently over the last few weeks, going as far as having to do an extended test. However, even after an extended test, my computer will no longer boot up properly. I can get to the login screen (taking longer than normal), but when I do, the mouse lags and I just get a black screen after I log in.

I’ve tried doing everything else I could think of and what had been suggested and nothing has worked.