Help with levelling an asphalt floor.

Hi,

please could someone shed some light on this situation as I’m getting confused.

I have a 1950s house with no DPM. Instead it has an asphalt screed (10-20mm) on top of a concrete base.

my issue is I want to level the entire floor but there used to be a fireplace which has been taken out and there seems to be just concrete levelled to the top of the asphalt.
What are my solutions here? Will anything adhere to the asphalt screed?

Iv been told ardex NA will but after speaking to ardex they said it will crack where it meets the concrete and it’s just confused me.

Any help greatly appreciated.