Mold in the basement is a serious problem, and it is important not only to get rid of it, but also to prevent its return. My advice is to start with a professional assessment of the situation. I contacted servpro and they really helped. These guys specialize in mold removal and restoration and repair work. They thoroughly cleaned everything and treated the walls with special compounds that prevent the reappearance of mold. In addition, they gave some useful recommendations on ventilation and insulation of the basement, which turned out to be a key factor in the fight against dampness. The repair went smoothly and the mold did not come back!