OK. Admittedly, I do not really understand relations. So if you could fix it that would be amazing. I tried replicating the relation with the Beatrix school.

Here is my attempt at making the roof: changeset/172398149

So if you go there in person, the building on southwest side (originally detached) is actually attached to the main building. But it's like a separate building and then a roof between that separate building and the main building. So maybe the proper way is to mark the roof?

They aren't segregated. Maybe pressed wrong button in StreetComplete?

So I finally got out there again, and their office building definitely has number 7 on the window. I can upload an image somewhere if you want.

I'm not exactly sure. What I do know is that this building has "Selhella 7" plastered on the window.

https://en.ja.is/kort/?page=1&q=icetransport&x=354024&y=397292&nz=17.00&ja360=1&jh=58.1

Looking at the street view puts Hertz to the right of that building. This just makes the map more confusing. The main reason I made the comment is because the shape of the building marked as Selhella 9 matches the shape of the IceTransport building. But then what's the L-shaped building between Hertz and the current building marked as IceTransport?

The website of IceTransport shows their address as Selhella 7. The number on the outside of the building also says 7.