Prep advice on block and beam floor

[Fred2020]

Hi, after some advice, doing some renovations at a house we’ve just moved into. Knocked kitchen/diner into 1 room, took the tiles up from the existing kitchen and there appears to be a hump in the concrete screed, it’s a block and beam floor, put level on the highest point and there’s 6mm gap either end of the level. There’s a few hairline cracks too. It’s approx 6.5m x 3.6m.

We have got some 800x800 porcelain tiles to lay

Question is what’s the best self levelling to use to get it all flat, and what shall I do about the cracks? I’m sure they’ll be finished moving now as the house is 8.5 years old.

Thanks.