subfloor smells

Hi, I'm looking at installing some laminate in the living room of a newly purchased house that was built in the 60s. When I took up the carpet there is a strong must smell and large cracks and debris near an external wall (see pics). The floor is concrete with black tiles (vinyl i guess?) How would I go about fixing this. The rest of the floor seems to be in good condition. Thanks in advance!

Just mix up a cement mix, ³ sand to 1 part cement