I'm sorry to hear of the various issues you're experiencing.
The first steps would be ......
1. Clear Cache Files from the phone's System Partition Section > https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/ You may need to insert your earphones or hook upto a powered On Laptop to access the Clear Partition Section. This may help with lag or stutters as this clears the phone of old/unused or broken cache files.There is also a Repair Apps option in the Menu System too.
2. Safe Mode > https://www.samsung.com/uk/support/mobile-devices/how-to-start-my-galaxy-device-in-safe-mode/ turns off downloaded apps and themes etc which may highlight an app or theme that's causing conflict.
Let us know how you get on please.
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "