Samsung galaxy s21 super laggy, slow and BT-frustrations

[Jojokrog]

My samsung galaxy s21 has been frustratingly slow since I got it in February. Is this normal? I can't play YouTube videos smoothly in HD, browsing anything in chrome actually feels as slow as browsing on my smartwatch, and I useually dont get any notifications from apps unless I manually open them. And my phone litterally laggs with no apps open when I pull down to see my notifications, and opening the tab to see media devices litterally takes up to 3 whole seconds to respond after I tap it (imo it kinda defeats the whole porous of having a quick-menu - if it's not quick at all) and my phone will verry easily lock up on the homescreen with no apps running in the background with cashe freshly wiped. No, I have not filled up my storage. 

Also, bluetooth on this thing is a nightmare. It autoconnects to everything I DON'T wanna connect to, and has only successfully connected to any of my three different headphones TWICE without me opening the Bluetooth-menu and doing it myself🤨 

This bothers me to the point where i linked up accounts on here to write this post, because I don't even use my phone heavily and it feels like Im using an old and unsupported device at times.

[antikythera]

Have you tried a factory reset? I know it sounds drastic but given the problems it may be worth the pain of doing so. Backup your important files, videos and photos first because everything will be wiped in the process

[Glenntech]

Yeah you have something on your phone that's dragging back the processing.
Have you tried putting the phone in safe mode and seeing if that's speeded things up. If so you will have a third party theme or app that's slowing your phone down.
Going into battery and device care and seeing what is using the battery the most may give you a clue ss to what is background running all the time.
As the other answer, backup your data and do a factory reset as by the sound of things a Partition Cache wipe probably won't fix it. But there's no harm in trying that if you want before a factory reset.
If you factory reset, setup the phone and see what it's like before you load any third party themes or things like gaming apps.