Issues removing wallpaper

[SusanRT]

Hi, hope I'm posting in the right place for this.

We moved into our house a few months back, and the wallpapering generally wasn't great (e.g. Peeling, bad corners, etc). I've begun on our small bathroom removing the wallpaper with the intention of painting it instead. Slowly getting there! However I've hit some issues. Plaster has come off, not masses, but I'll need to replace it, and in parts there wasn't even plaster in the first place. A bigger issue, I think, is that at some point someone has nailed up board to the corner of the bathroom and wallpapered over it. I can't just paint over it. How do I tackle it? Do I cover it in something before painting, does it need removed? Picture attached (hopefully)

 

[stem]

The hardboard should be removed and replaced with suitably secured plasterboard, then the whole area should be skimmed with new plaster.

 

[Bosswhite]

As its a Bathroom and a small area, it would probably be better if you got a Plasterer in to reskim the walls
Shouldnt be more than a mornings work