So I consider €1700 to be affordable, that still leaves you with over €2000 per month to live on after additional costs and the cars are already paid for by the employer. Personally, I even see potential for special repayments if you want to. But lifestyle is always a personal matter.
With your financing, you have 2% interest, 2% repayment, and after 20 years you will have paid back almost exactly half. You will certainly manage that again with the follow-up financing and I also do not expect that you will pay much more than 2-3% interest then. For me personally, however, the term of the loan overall is a bit too long and I would try to shorten it either with a higher rate or special repayments.
The total amount of your costs sounds plausible, the internal distribution is certainly not correct. The carport kit is available for significantly less, but in the garden you will almost certainly spend more than €10,000 on rental equipment and materials.