As we have discovered in this forum, the logout problem can be due to any number of things. You might try using Firefox as your browser, as it has its own cookie cache. Most other common browsers (Chrome and others using the Chrome engine, like Edge) use a common cookie cache. However, at least one Firefox user has encountered this problem. You might have created this problem by using certain browser options like "clear cache on exit" or "private browsing" or by using certain PC "cleaning" tools. My problem was caused by Google Chrome Elevation Service. I disabled it and the problem was solved. Later I re-enabled it to assure Chrome updating, but the problem has not returned. Maybe it was broken and got updated.
I don't have an easy answer for you about your files disappearing. Could be malware. Maybe they got moved to the cloud, if you have a cloud service such as iCloud. If you want to search your hard drive or SSD for them, be aware that some folders hare "hidden" in Windows Explorer and you have to change a "view" option to make them show, or even appear in a search. Be aware that when you mean to copy a file using drag-and-drop, you may remove the original. I have noticed that drag-and-drop with Windows Explorer now "moves" instead of "copies." If you saved your now-missing files to other media (flash drive, external drive, cloud) you might have inadvertently "moved" them. If you had done that, I assume that you would remember the backup. However, this is a good reminder to always back up your files, preferably to two different places.