Is the price for the prefabricated concrete garage okay?

Our offer from two providers for a comparable garage is also in the range below 10,000 euros including delivery and on-site installation.

A bit off-topic: what should one expect to pay for the two strip foundations?

Garage with foundation 10-12000 € in size is reasonable. I paid 10300€ in 2014 for 4.50x9.30 with an electronic door, one door, two windows, flat roof and foundation. Delivery and installation were included.

Tree specialist, but that's cheap.

What kind of garage? Where from and satisfied?

Unfortunately, we were persuaded to sign with exclusive garages. Luckily with the clause that free withdrawal is possible at any time.
Because they are not well rated. But none are really.
Even Zapf is rated very poorly.

Our somewhat extravagant garage with about 50sqm I had quoted by Kemmler because they are practically local. They want just under 50k for it. SF with sectional door, extensive green roof including setup without foundations. A side door costs just under 2700 net )) I would be very grateful if someone could recommend a cheaper provider to me.

From the local carpentry company, timber frame construction plastered on the outside, managed to negotiate down by about €1700 to €10300. Other carpentry companies were similarly priced and got back to me after the season. Everyone initially complained or laughed at my price expectation, the building season ended and my phone rang. I just had to wait a while but at that price......

I got my somewhat extravagant garage of about 50 sqm from Kemmler.
I would be very grateful if someone could recommend a cheaper provider.

Do you know Den Bergle in Mühlacker?

I had a Grötz garage offered from them, size 6x6 including a 5-meter door, one window, one door for about 15,900. Strip foundation about 3k and crane per hour about 120 euros.

But then I preferred to have it built by a few skilled workers from Bulgaria, whom I found in your construction area. I can give you the address.
The formwork was pushed away during pouring though.

With my own work "window, door and parapet," I ended up at about 15k fixed and finished.