ᐅ Drywall is crooked, uneven, and poorly plastered – how to hang wallpaper?

Hello dear forum community,

As mentioned in the headline, I have everything imaginable in my new room.

Now to my current approach. So far, I have tried to remove the old wallpaper, but it hasn’t worked very well, as several layers of paper remain. I will try to remove everything completely without any residue.

What has come to light is a very poorly skim-coated drywall (bad plaster used with cracks, holes, and uneven transitions) that has very old and rough plaster on the corners, which is porous and crumbly.

I would like to wallpaper this wall again with standard wallpaper, but first prepare the entire surface properly.

Now my question to you: How exactly should I proceed and which products should I use?
- Remove all wallpaper residues from the wall completely
- Repair and smooth all holes, or plaster the whole surface with a thin layer of plaster instead?
- Sand and apply a primer?

The problem is also that the drywall panels have beveled edges, so the wall is not perfectly flat.