Restrained retaining wall design

Hello,

I'm working on the design of a retaining wall, on which a steel hall will be mounted.
The retaining wall is not beneath the whole perimeter of the building, but only for part of the columns, as the terrain is inclined at a certain place.
As in my country's code is not clarified the situation with a hall, building, etc. above a retaining wall and I'm not yet experienced with this, I really hope I'll find some help here.
What I do now is to make calculations of the wall for 2 stages:
1) stage 1 - only the wall and the backfill - before installation of the slab and the hall - here everything is clear for me - I'm making the stability checks for sliding and overturning of the wall, check for the soil stresses and calculating the necessary reinforcement of the wall;
2) stage 2 - installing the slab and the mounting the hall (it will be pinned to the foundation). So for this stage the main question is should I check the wall for sliding and overturning as it is already restrained by the slab? Can I assume that the horizontal force from the hall goes directly in the slab? Than for calculation of the soil stresses I should take only the vertical loads. And what about the at rest load from the backfill - I suppose this horizontal loading can not goes also in the slab, can it?

I hope I explained it well.
Thanks a lot for all the replies in advance! I really have not any info in our code here..
See fast sketch here and in attachment:

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Regards