How do you wallpaper a drywall panel? How do I fill in the indentations?

Yes, we did it that way too, or rather my husband wrote it better. But I am a big help. :D

Thoroughly scrape off beforehand and we also applied a special primer.

Yes, that's true, it's an easy job. I have already done that with my husband. Remove the old wallpaper completely. Then fill in the unevenness and prime.

After that, the wallpaper goes on. I am responsible for the glue and brush the wallpaper strips. They then need to soften a bit and absorb the glue.