I was so into work, that I forgot to take pictures step by step. Our next step was to make the connection between ground/foundations and walls. So we bought prestressed concrete planks (3.0 and 2.5 m long, 5.0 cm thick) and I cut them, so it fit between foundations. All the gaps were later sealed with elastic frost resistant cement glue.
Now it was possible to close the walls. South, west and east walls are closed up with same polycarbonate plates as roof. North wall is made of 20mm wood board + 100 mm glasswoll insulation + 20mm wood board. Well, I found local manufacturer of profiled wood boards. It’s much cheaper this way and money stays in local district.
After first wall was built, I did electricity box with consumption meter and LED lights (3x 10W reflectors), keeping in mind we might install solar panels later.