urgent help on a dedicated server

My Ionos server is full. I can't access my plesk, I can only get to it through SSH. But I'm not a server administrator and I don't really know what I'm doing. I don't know what caused the partition to fill up. I don't know if it's database related or files like images... I need to make space so I can get plesk back up and running but I need help to pinpoint what is taking up the space. This is for work right now, urgently.