ᐅ Sandstone - Basement Floor Stains

What are these spots on the floor? Additionally, there is black mold on an interior wall in the basement. Furthermore, there are salt crystals on the wall that look like small hairs. The stains on the wall, which are brown, are also present.

Efflorescence and mold are signs of moisture in the masonry/concrete floor and should be remediated in the medium term. Causes must also be addressed, such as hydrostatic pressure from outside.