You cannot revert.
What you can do is sweep your device clean.
- Backup WhatsApp/Signal/Telegram if you have it/want it to be backed up
- Set Google to backup and sync it
- Copy all your pictures and what not to SD card
- Make a backup with Xperia Companion
- Reset your device on the device or do a software repair with Xperia Companion
Now that your machine is at the brink of a renewed life take a good look at which apps you really use and want to restore.
Keep it lean and clean.
Speed regained.
