Macbook Pro 2011 loud fans and slower performance

[Mr. 123]

Hi everyone,
I have a macbook pro 2011 (early) 13 inch with 16 GBs of ram and an SSD hard drive. Yesterday, a security update for El Capitan was released and without me accepting it, it was installed on my computer.

After the update the fans were running all the time. When starting the computer, when browsing etc (not cpu or ram heavy things). The computer also felt a bit slower. I tried resetting SMC, PRAM, first aid (on the disc) etc but nothing improved.

I then went on to restore from a time machine backup (which I had of computer the day before the security update was installed) and now I'm back in the previous version again. However the fan is still really loud and the computer is still slower than it was before. In the activity monitor I saw that something called WindowServer is taking a lot of CPU and there's also something called coreaudio.

I don't know what to do and I'm kind of panicking because I use the computer for music production in Logic Pro so I really need the computer to be fast.

Please let me know if you have any suggestions to what I could do to get my old computing experience back!

 

[Mr. 123]

Update# I did the 1 hour hardware test on my computer and it showed no issues or damaged hardware. I'm guessing the issues are all in the software so would reinstalling El Capitan (without loosing any data) be a plausible solution?

 

[Mr. Retrofire]

Update# I did the 1 hour hardware test on my computer and it showed no issues or damaged hardware. I'm guessing the issues are all in the software so would reinstalling El Capitan (without loosing any data) be a plausible solution?

See
https://forums.macrumors.com/threads/should-i-care-about-dust.1745715/#post-19244169
and
https://forums.macrumors.com/threads/15-retina-noisy-right-fan.1754947/#post-19377137