Home button , multitasking app button stopped working , no notifications

2 days ago, because the device was full, my phone suddenly stopped working, the last message it was showing was Google Drive abruptly stopped or something like that. i was able to delete photos that were backed up on Google photos i restarted the phone only to findd the Home button, currently open apps button andd dnotifications not working at all. my phone simply vibrates when i get an SMS, whatsapp msg bt doesnt show on home screen any notification I have to manually go to SMS/whatsapp to check if there are new messages. i tried clearing cache in storage and rebooting multiple times - No luck!
also gmail is not updating automatically.

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