> First I tried to install High Sierra again, I thought it might have bugged on the last install. Nope.
> Then I backed up everything manually to an external hard drive and installed High Sierra from the scratch like I would be selling my mac, meaning I would have to install all my apps, fonts, and so on again. Did not help.
> After that I googled a lot how to do "downgrade" to the older version which Apple seems to made hard if you don't have experience with terminal or don't know about formatting but when I Followed multiple tutorials I managed to it quite easily but took a long time.
I did this last night and I can't promise I remember all the steps right way but shortly this is what I did I downloaded old os, made a USB stick installer and wiped everything in my computer. Found some good instructions here:https://www.macworld.com/article/2981585/operating-systems/how-to-make-a-bootabl e-os-x-10-11-el-capitan-installer-drive.…
1. Backup everything
2. Double check you backed up
3. Download the el capitan from App Store
4. Format, rename and partition 8-16gb USB stick the proper way (link up there tells everything^)
5. Move the installer to the formatted stick
6. Restart the computer with special command, erase everything from the hard drive (the link I posted did not mention this part so when I Rebooted with command + r and used disk utility to erase my hard drive (it will pop up macOS recovery with this command: About macOS Recovery - Apple Support)
7. Rebooted again with command + option to Install El capitan from the stick (the stick wont show with command +r )
8. Hope, pray and sacrifice your soul then wait that the installation goes all the way to the end and for me this took ages, it looked really worrying once in a while with looong stops only white screen showing or text saying " about a second left" meaning 20-30 minutes but IT WORKED.
No screen problems, ghosting or "burns", no lagging, no pinwheel of death at the moment.
