Performance issues iphone 11

Half a year ago I bought the iPhone 11 and after just three months the phone started bugging and acting weird. It randomly started closing apps and it would go to an all black screen with just a white little loading sign on it. This took around 20 seconds and then it was 'solved'. But it started to show up more and more up until the point i can barely use my phone because every half hour it does this thing. Every time it stops loading and i touch the screen again, it immeadiately goed back to the black loading screen. The times i do have the chance to unlock it more than half of my apps are gone or the places they have on my screen are blank. But i barely get the chance to unlock it because i have to shut my phone off completely to let i function a little again. Most of the times i have to shut my phone off for like four times in a row to get all the bugs to dissapear. At this point i cant even use my phone anymore and i paid a lot for it so i am pretty upset about it. I hope you can help me with this problem.