The better your initial diagnosis, the fewer surprises you will have during or after your renovation.
If your walls are uneven or have cracks, you can first remove the irregularities with a hammer and chisel and then treat the cracks to solve the moisture problems and prevent them from reappearing. If the irregularities are too large, it may be necessary to redo the plaster. The recommended treatment is the application of filling plaster, the application of calico, then the application of finishing or smoothing plaster and finally the application of primer.
It is possible to test your walls for moisture content with a moisture detector. You will then be able to choose a special bathroom paint. The lighter the paint will be, the more it will enlarge the room, the darker the colour will be, the more it will give a cocooning atmosphere.