For malware, I'd boot to Safe Mode and do a full scan with an up to date antivirus. Then I'd download MalwareBytes (free version), get it up to date and do a scan with it.
Now for IDs. If you save something in one of the folders for a given user ID (e.g. Downloads, Documents, etc.), then reboot and use a different user ID, you're not going to see those documents because each ID has its own set of folders. Have you checked for this?
Of course you can always take Dafydd's suggestion to restore to factory settings and not worry about what you've lost. Bear in mind that you'll have to reinstall any software that didn't come with the laptop when it was new. That means Chrome, Office, and whatever else you've installed and anything that the store installed after they got it.
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When you've gotten your system back like you want it, I urge you to get yourself an external hard drive and a good 3rd party backup program. You can set it up to do everything automagically at the time and frequency of your choice. 1 TB external hard drives are about $50 these days and a really good FREE backup program is the Easeus Todo Backup Free. That can save you a lot of time and frustration the next time something like this happens. Sooner or later it happens to all computers for one reason or another.
Good luck.