It sounds like you have a "Peelable" paper. With peelables, the facing is peeled off leaving a paperlike backing still adhered to the wall.
Take a wet sponge and wet an area of the paper and keep it wet for about 10 minutes, then gently scrape with a putty knife or a small taping knife.
I remove this stuff by spraying water on with a garden type "compression" sprayer, soaking an area large enough to keep wet for about 15 minutes. Then I wet the next area and allow it to soak while I remove the paper in the first area.
You should take the time to be certain that all the paste residue is removed. Rinse the walls with a sponge and clear water several times and change your rinse water often. You will be able to tell if the residue is removed by running your hand over the wet wall and then see if you hand feels "slimey".
Hint, I use a "Clamshell" sponge for this task. It's large enough to cover a wall in a reasonable amount of time. I also use an emtpy 5 gallon pail to hold about 3 gallons of rinse water. Most household pails arent large enough to get the job done quickly.