0klyla Sorry for the late reply. If you still need help, please provide a dxdiag. Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop. From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.
You can also remove Options.ini from Documents > Electronic Arts > The Sims 4 to reset all your in-game settings, including the graphics settings. That should allow you to play on the default settings again. But switching to High shouldn't cause crashing either, just maybe bad performance, so I'm curious as to why this is happening in the first place.