ᐅ Completing the bathroom / exterior wall is not watertight

Hello, we have an extension. The exterior wall there needs to be resealed because we have over 70 percent humidity indoors. This will unfortunately only happen at the end of September. Now my question is whether it makes sense to start renovating the bathroom (currently planned) at least by applying a liquid waterproofing membrane and tiling the floor... What do you think?

Wouldn't it be better to start with the walls first? I watched our tiler, and he also applied this "sealing tape" at the corners between the wall and the floor... it's hard to see in the picture, but it's that dark strip.