Sanding walls in living room with electric sander

[diy.newbie]

Hi, i am sanding my living room walls with an electric sander in order to paint them. I am so far working on a small area of the wall and there seems to be 3 layers of paint, then by chance some pink stuff with i assume is gypsum has started showing a little in some areas, i am i wanting to get right down to the gypsum and how do i get the third layer of paint off when it is only easily coming of in some areas? In the end can i paint my chosen colour straight on to gypsum or would in need a neutral base colour like white?

[stoneyboy]

Hi diy.newbie
Where you sand through to the plaster it's worth applying a watered down coat of paint to seal these areas before you apply further coats.
Regards S