2. Is IMHO cheap to okay.
3. Depends (precast concrete garage or steel garage? Which door? Including foundations? Etc. pp.) -- Depending on that, 10,000 euros can be extremely cheap or just barely okay.
5. Hard to say, bathrooms are always twice as expensive as a normal person would expect (sorry, my very personal experience with bathroom suppliers). Here you need to know what the basis is ... Is your special request just a bigger sink or does the whirlpool already belong to it?
HTH