Ok Mampara. What you need is a paste called Vinyl Over Vinyl or V O V for short.
Carefully peel back the paper and again check the lintel for loose surface or mould if ok, wet the lintel with a wet sponge or water spray bottle because moisture from the paste will be absorbed if the lintel is too dry.
Brush "V O V" on both the lintel and the loose paper's surfaces.
Now you need a flat 6inch wide blade or plastic spatula type implement or blade.
Press and smooth the paper with the blade being careful not to damage the paper of course and smooth out any lumps or bubbles.
Clean any excess V O V that oozes out with a damp sponge and keep pressing and smoothing it out again clean any excess adhesive with the damp sponge. V O V is murder to get off when dry. OK.
Because it is vinyl paper you can use a heat gun or good hairdryer from a distance of about 5 inches.(be careful with a heat gun).
After about 45 seconds with the heat treatment , make sure that you can apply good pressure to the area with a smooth flat surface for a few minutes. Then using a clean sponge again wipe the area down. Job done.