Who to talk to re inspection of cracks and possible foundation issues

Noticed this crack in the ceiling in the hall in the middle of my house. It continues in the rooms to either side, but is less significant. There is a water tank near it in the attic.

I have also noticed doors hanging at a slightly different vertical angle.

I have been concerned about foundation issues since I noticed that the soak pit on one side is directly under a downpipe. A solid patio also drains into this. The patio is connected directly to the side of the house and it looks like it is above the DPC. I plan to get a french drain and new soakpit installed when i can afford to do so.

I noticed some time ago that one of the diagonal supports in the attic had moved so it is not flush with the roof wood piece that it supports. That has not moved since i observed it a couple of years ago. It is roughly in line with this crack.

It is a one-off build on a floating slab foundation.

I want to get a professional to look at this and advise if any repairs or changes are needed, as well as to validate my existing plan to address the drainage and patio issue. What sort of professional do I need?

Thanks in advance.