My screen layer is coming off

The usual cause for a screen coming off the body of the phone is a swelled battery pushing it off from the inside, but with your phone the battery is on the other side of the midframe so it shouldn't be able to. I'm guessing age plus possibly stress from being in a pocket maybe, unless there has been some other source of damage such as being dropped.

Anyway, you'll basically want to follow the screen replacement procedure and remove the screen, clean the old adhesive off the screen and frame, then glue the screen back on as shown in this video.

How to display change replacement Samsung Galaxy M11 - YouTube

You'll have to buy some glue and have some 90% or higher concentration isopropyl (rubbing) alcohol for the cleaning, along with some cotton swabs, but otherwise there aren't a lot of special tools or equipment needed outside of a small Phillips screwdriver.

Hopefully that'll get you going; good luck and let us know how it goes!