I repair the machine before anything else because it could be far too hard to fix if there is broken parts.

I read your machine is dual booting. Nice but I find support to be lacking for such systems. That is, no one has a definitive procedure to correct dual booting failures that works 100% that does not involve reloading the OS or OSes.

I'd take this as a lesson about dual booting and pick the one OS I want to run and stick with it. To save files I usually pull the existing HDD, put in a blank drive and install the selected OS on that. Then the old drive is put into some USB case for the owner to get at the files if they forgot to backup.