You can restore them from a backup, if you have any, otherwise, you could try data recovery software to recover the deleted stuff. Degree if success will vary, so there are no guarantees. I've always adviced against using programs that seek to "clean up" or "optimise" a PC because in the hands of non-advanced users, they can cause more harm that good. Stay away from such "one-click fix all" programs, you don't need them, and if you choose to use them, then make sure to scrutinize each option they present before enabling them. Blindly running such utilities is very unwise, as you've found out.

Could you help me with finding and installing the backup folders? I tried to find them but had no luck. Doesn't Thunderbird do an autobackup?