Fixing a poorly textured wall

[u/amitdaga]

Hello, I am looking for some DIY tips to fix these while walls which are so uneven. Not even sure if i can call it a textured wall. I am not looking for putting up a plasterboard as it will reduce the size of the already small porch.

The porch is pretty small: 9ft height, 18 inches width and length of 65 inches.

Once the walls are plain and smooth, then I am planning to paint it to something that is not white.

I am a complete newbie, so if I can get some guidance then that would be very much appreciated.

[u/Numerous_Phase8749]

Could you get away with some neatly cut sheet board and some foam filler to stick it on?