Show the affected part and its place around the shower, bath or window. Identify grout, sealant, tile or a painted surface rather than describing everything as a dirty wall. Say when you noticed the marks and whether they have returned after earlier work. Mention products already applied and known plumbing or extraction difficulties. These details start the enquiry without diagnosing the cause from a single photograph.
A general clean of bathroom tasks has a different scope. Request mould assessment directly rather than assuming ordinary limescale or soap-residue cleaning covers treatment and moisture concerns.