Should i caulk before applying lining paper

I wouldn't paper over caulk or anything slightly flexible as it won't adhere well.
Once the lining paper is hung then caulk after the first coat of paint.

 

When you say not great how bad are they? I would suggest making good with filler.

 

Was also wondering what the issue was
Just wondered if it was the usual cracks

If corners aren’t square, you ain’t gonna square them up by using caulk then

Better off using a powdered filler, any brand really will do the job. Toupret Interior always highly recommended on here. EasiFill is ok, works out good value if using loads as comes in 5/10kg bags. Some peeps like it as a filler, sands easily but is a little sticky when using it

Fill corners as needed, sand down smooth and square and keep that nice, crisp 90 degree corner

Caulk is good if you’ve got cracks between walls and ceiling junction but again, don’t overfill with caulk or you loose that angle

Size the walls and especially filler before going with the lining paper

 

Try and avoid it, but if you do have any slight gaps after the paper has been hung, apply any filler sparingly after the first coat of paint.

 

Corners are never ever square, you need to lap it around the corner and as it's only lining paper cut it into the corner, when all the room is lined and dry caulk it from top to bottom.