Re: Sims 4 background of sims turns black then app closes
@aegisquared It sounds like you might not have accessed the Startup Repair mode, the recovery mode I mentioned earlier. Here's a better description:
If that doesn't help, I think you need to get someone to look at the computer in person. Whether that's a professional or just someone who's good with Windows, this is the kind of problem that needs hands-on help. It may be that you need to reset the computer or reinstall Windows, either of which would delete your data. There are ways to grab your essential files first, by creating a bootable USB stick and booting into that rather than your computer's internal drive, but again, that's something that you might need to ask for help with.