I intended to build 2bedroom semi-dettached. I have just completed the foundation with 3couches of 6inches blocks. But now, I like to change my plan to the same design of 4units 2bedroom flats (i.e 2units downstairs & 2units upstairs)

Kindly help me with your advice:

(1) Is it proper to convert 6inches blocks foundation to DPC (german floor) and how? List steps

(2) Any other advice you considered necessary for me?