Height new concrete floor

Rectangular standalone shed 475cm x 305cm.
Old solid concrete walls with the exception of the front wall.
Front wall single concrete blocks unplastered.

The galvanised roof now needs replacing.

Concrete floor is below patio by approx 10cm.

Floor is prone to dampness along the front wall. Floor is very unlevel and cracked.

Best option is to remove old concrete floor and install new one with a damp proof course?

How high does this new concrete floor need to be?
The shed only has internal height of 198cm...(6 and a half foot).

Many thanks

Does the exterior floor slope away from the shed?

No. It slopes downwards towards the shed. Any suggestions?

What is the shed foundation made of? In my opinion, the proper way to mitigate water intrusion is to make that shed at or above grade. Is their any way to add a 10mm - 12mm block or pressure treated lumber to raise the base of the walls?