How to remove LOTS of wallpaper bonding agent? I am remodeling my basement.....resourcefully when I removed the wallpaper from the...

I am remodeling my basement.....resourcefully when I removed the wallpaper from the stairwell there is close to 1/4 thick cement residue underneath. I tried sanding it and using vinager and hot marine, nothing seem to take it stale. I mean you can see a few spots of the imaginative paint but not a whole lot. It's highly think and course. Any philosophy??? I heard to use DIF but will it work for this much epoxy resin????? I have never see so much glue used back I guess the previous owners planned on having this wallpaper for life span?! LOL
Custom made curtains/drapes?
Answers:    Try some TSP, but be sure to wear gloves when using it. You can purchase this at a wallpaper store or most Walmart and hardware stores carry it.
What open-handed of paint can i mix within...
Diff works great, but you may enjoy to let it soak for a while. I have difficult to remove wall paper, and have to do numerous sprayings, but it eventually came stale. Good luck