How to fill and level an uneven backyard?

[simont]

Hi, I just got keys to my place, and I need to perform some basic landscape at the backyard.

Currently, the backyard is uneven, and its level is much lower than the finished floor level. I am thinking of filling and leveling up the backyard and have it all covered with lawn with a garden bed running along the boundary/fence.

Seeking some advice on the following:

1) What's the best material to fill up? I was thinking just the usual topsoil will suffice?

2) Are there any other works/tasks I need to perform, or just simply fill it with topsoil to the required level will do?

3) Size is approximately 3.5m (width) x 6.5m (length) x 0.35m (height), equating to 8 cubic meter. Do I need to factor in any compression factor to estimate the amount of soil required?

4) With the black plastic liner (the liners that are part of the concrete slab), can I put soil above it, or do they have to be 'lifted up' and 'tucked' next to the slab?

5) Around the sewer riser, there is a deep depression, presumably left by the builders when connecting to the sewer line. Any different requirement to filling it up around the riser, or topsoil will do?

Photos attached. 

Plastic LinerPlastic LinerBackyardSewer Riser

Thanks in advance!