The reliable way to hire a tradesperson

Hello, the subfloor in the dormer of my terraced house needs attention, it has some soft spots. However I’m struggling to know which tradesman would be able to do the work. Would it be a joiner or a builder? Hoping someone can advise.

Hi. I noticed some circular and small damp marks spread on the wall of one of the bedrooms. As there are no gutters on that wall outside, so no water source from a clogged gutter, I wonder if the problem is with the old brick joints outside? Maybe is time to repoint the wall outside? Any help/suggestion is very welcome. Thanks.

My bathroom fitter has lined the shower and bath areas with gypsum plasterboard and intends to apply a tanking solution to provide waterproofing before tiling. is this acceptable practice? my expectation is cement board plus tanking, or at least aqua-board plus tanking. who's correct? Also rest of bathroom has been left with the original plasterboard on walls and ceiling. the walls will be tiled but should these also be aqua-board?