Which roof for garage?

Hello,
Which roof would you recommend for my garage 9x6 meters? The back two meters are separated as storage. So free span maximum 8 m.
Concrete ceiling would cost 5000-6000 euros.
I would like to have the ceiling cheaper and do it myself.

We neither know your house nor your development plan. Your house is relevant in the sense that, in my opinion, the garage should not appear too blatantly foreign next to it; and if it is on the boundary, a medium wall height would usually limit the height of the roof structure. Viewed on its own, a truss construction seems favorable and neat to me – but aesthetically, this is hard to judge if you don’t know the house.

I always "get annoyed" at how, next to houses that are styled down to the last detail, some shoeboxes for the car (or even worse, bulky waste with the car parked in front) are placed, which look from the moon like "there was no emotion left for this" :-(

So the house is nothing special. Square with a gable roof.

A regular concrete roof only differs from a wooden roof by a covering strip on the side. From above, you hardly see it anyway.

I've seen something like this several times and don't think it's a shame.

There is no development plan and the height should be about 2.2m inside.

How would one construct the roof with collar beams? Do you build up 2.5m high and lay them across, or at that height do you always leave a niche every 0.5 - 1.0m and place them in there?

How would you construct the roof with collar beams? Do you build up 2.5m high and lay them across, or do you leave a niche at intervals of 0.5 - 1.0m at that height and lay them in there?

Yes, the substructure must then be made with beams. I'm just not sure what goes on top. Wood, insulation, and bitumen? Or sandwich panels? Or something else?