[Closed] kitchen flooring help - damp?

Right here goes.
I'm about to fit a new slate tile floor in the kitchen. but I've run across a problem.
The old floor is vinyl. I've pulled that up to find slc underneath.
over the 20sq meter floor, 90% of it is brown and patchy like there is/has been moisture under the vinyl.
The garden is 1mtr below the house and I can't see and signs of dpc 😕
The exterior wall is smooth rendered up to the height of 50cm, the rest is pebble dashed. almost all the smooth render is blown 😕 so it looks like that needs to be hacked off and reapplied.
whats the best course of action?
getting the exterior wall fixed first is the main thing then sorting the damp floor. is it worth just laying the floor anyway? sealing it with epoxy then laying over the top?