Question
Hi, I was wondering what are the best houseplants for a small flat with
excessive air moisture and low amounts of sunlight?

Answer
Mark,

Most tropical house plants would be quite happy in your flat but they will not remove the excess moisture from the air. They would enjoy it but they do not remove it and only a few plants would be happy with the low light. Those that would are:
Peace Lily
Dracaena 'Janet Craig'
Chinese evergreen
Pothos Ivy
Philodendron Selloum

However I think you really need a dehumidifier. Good luck.

Darlene