"Bookmarks and history system will not be functional" with corrupt files found by Avast and websites loading slow ONLY in Firefox

Question

Firefox is the only browser that lets me connect with my microphone. I need to use this feature for an online class. Earlier this evening, the message prompting me to allow or deny the class website permission to use the microphone stopped appearing, and without it the recording won't pick up any sound and I can't record anything.
I tried exiting and restarting Firefox. I had some extensions in use at the time, in particular Session Manager. The allow/deny message still wouldn't appear, so I restarted my computer.
Now when I open Firefox I see the "The bookmarks and history system will not be functional" error message. In addition, the browser loads websites extremely slowly; it takes several minutes to load each page or for me to be able to click on anything (the URL bar, the menus, etc) My other browsers (Internet Explorer and Chrome) are running normally and load websites at a normal speed. I tried downloading the latest version of Firefox but it didn't fix anything. I also tried restarting the computer again but that didn't help either.
I ran my Avast software system check and it turned up that the following files under "C:\Users\(me)\AppData\Roaming\Mozilla\Firefox\Profiles\Irozixj7.default" are "corrupted and unreadable":
-cookies.sqlite-shm
-cookies.sqlite-wal
-localstore.rdf
-places.sqlite-shm
There was one more problem on the scan, but it probably isn't relevant: for the file "C:\ProgramData\Microsoft\Windows Defender\Definition Updates\{9A2C6FA7-E04E-4819-B86A-8363A9D1E42A}\mpengine.dll" it says "The system cannot find the path specified." When I attempted to follow the path indicated, one of the folders (I can't remember which) said something along the lines of "You can't access this folder, do you want to permanently allow access to this folder?" I said yes and was able to access the folder.
I have tried to add the Places Maintenance extension but the speed is too sluggish to download anything. Trying to access any of the menus results in the browser freezing for several minutes then unfreezing but with the menu still unopened. Therefore none of the solutions found here (https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional?esab=a&as=aaq) seem to work.
My questions are as follows:
-Is it possible to figure out what caused the problem in the first place?
-Is there a way for me to fix it without losing my bookmarks and history?
-How can I avoid this happening again in the future?

Answer 1

First, I recommend backing up your Firefox settings in case something goes wrong. See [[Backing up your information]]. You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder. To quickly access this folder:
Help > Troubleshooting Information > "Show Folder" button
Next, keep this folder open, exit Firefox, and try moving the "corrupted and unreadable" files to a different folder. With the exception of localstore.rdf, which stores window positions, toolbar customizations, and other nonessential data, the other files appear to be session-specific files that hopefully are not critical. If you restart Firefox, does it behave more normally?
If not, try creating a fresh Firefox profile. It will have the Flash plugin, which is the control sites usually use to connects your camera and/or microphone, and other plugins, but otherwise will be a new setup. This article has the steps for starting up in the Profile Manager: [[Use the Profile Manager to create and remove Firefox profiles]].
If sites work normally in the new profile, you can import your bookmarks from your old profile, as well as copying over other files that don't seem to be causing the problem. Some trial and error might be required to determine that. This article has some tips: [[Recovering important data from an old profile]].
If the new profile is no better, you can exit Firefox and use the Profile Manager to switch back to your original profile.
Any improvement?