What can I do with a concrete subfloor from old lean-to?

Pulled down an old lean to because the timber was rotten.

I didn’t realise there was a raised concrete subfloor base that raised the height to the same as the kitchen floor (theres only 50mm to play with before spilling over the doorframe)

Now the concrete is always wet and puddled so I think it was never levelled or even with weatherproof concrete.

What can I do to both weatherproof and angle the surface to help drainage away from the house?

Tiles? Decking? Resin? A top coat of concrete?

Any suggestions will be greatly appreciated.