Advice on bringing life back to a garden

i’m trying to get soil/life back into my new tiny garden on a budget by myself. The garden is all paved. I have already removed a breeze-block wall that was next to boundary wall/fence. (Yes, 2 layers of walls). I want raised bed borders with a grass lawn but I don’t know the best approach considering drainage, effort/cost etc.

This is my current situation:

A: Dark grey concrete – maybe stained – tough concrete ~30cm below paving, probably only in patches

B: Tough light grey concrete – sledge hammer barely touches it, supporting a wall

C: Breeze-block foundation layer(?)

D+E: 5-8cm sand mix, 5-8cm hardcore mix

F: Tough light grey concrete – a layer above the paving – the garden is on a slope – could this be a retaining wall?

What next… Removing ~30cm deep seems bonkers / will need a pneumatic drill. (Access is through the terraced house.) Topsoil over the borders and work out the drainage? Do I need a professional?