Unsure of next steps after removing lining paper

[SmallSteps]

Just bought a house and wanted to get rid of lining paper to paint walls properly.

This is what it looks like at the moment. (Attached)

Had a bit of research and seems that top part is lime plaster, but not sure about bottom half? Is it cement or gypsum?

Should I sand all this blue paint off and then do lime plaster skim? To make the wall even before painting?

Thanks in advance!!

 

[Wayners]

Limelite plaster maybe. That's gray

 

[Harry Bloomfield]

Just bought a house and wanted to get rid of lining paper to paint walls properly.

Lining paper is usually used, to help smooth and hide imperfections in the plastered walls, to avoid the need to replaster.