Financing new construction of a single-family house in the Greater Munich area

Where exactly should there be any problems with that constellation? No envy at all: you come from a very well-off family. Money seems to be abundant in the family. If there’s a crunch with the bank financing, you just get another 250k from your parents and negotiate a very comfortable rate with them. You’ll inherit it all again anyway :) Honestly, I find the salary measly for the area. Even as a civil servant (I am one myself) you can significantly increase your income. You just have to step out of the comfort zone and consistently deliver above-average performance and apply + possibly do a part-time advanced degree. But I don’t see any pressure for you there given the above circumstances.

We ourselves live in a rental apartment of my father. Here we pay 600 euros rent. If we build, this amount would be given back to us as a gift.

1. 600 rent including utilities. Again: congratulations :)
2. I don’t understand. You mean the rental income from your father’s apartment will be transferred to you every month later?

Yes, I am aware that we are in a very fortunate situation. It even goes so far that I regularly feel guilty about it. I am tenured with A13. Before that, I worked in the private sector with a higher salary and, of course, better opportunities for advancement, but after careful consideration, I returned to research. Again, the luxury of being able to afford that.

I also think that 700k is somewhat underestimated for your plans. We are currently in discussions for construction in the LK Munich area, where the prices per sqm are mostly estimated at 3500 - 4000 €/sqm, with a strong tendency towards 4000. This corresponds quite well with the example from : 700k minus a flat rate of simply 100k for garage and basement = 3750€/sqm. Then add additional costs, etc.

Yes, I am aware that we are in a very fortunate situation. It even goes so far that I regularly feel guilty about it.
I am tenured with A13. Before that, I worked in the private sector with a higher salary and, of course, better career opportunities, but after much consideration, I returned to research. Also here, the luxury of being able to afford that.

You really don't have to feel guilty about that. No one chooses where they are born, I’m happy for you.

The financing itself – equity / loan amount and so on – also sounds healthy to me. Besides, you have the option to slim down the house a bit.
The construction costs estimated here in the thread knock the wind out of me, but that’s how it is – I’m currently building in RLP, and the clocks seem to tick differently here. But if it’s like that in Bavaria, you can always consider leaving out the basement / saving a few square meters.

I would get some concrete offers from construction companies / start research in that direction. Then you get a better feel for everything.
If I understood you correctly, the plot of land already belongs to you? Then nothing should hold you back from putting something solid on it given your financial situation.

Yes, I am aware that we are in a very fortunate situation.

Nevertheless, I would plan without a basement. At the moment, many things are uncertain, and quite a few builders are planning only 135 sqm instead of 150 (or similar, at least significantly less than 170 sqm and without a basement).
On top of that come increased property taxes and rising utility costs. I would plan for 700€ per month instead of 400€, and 1000€ for mobility. Nevertheless, your project is feasible. The basement replacement room can be well accommodated in the already existing roof space. With a fixed staircase, a good alternative.

Yes, I am aware that we are in a very fortunate situation. It even goes so far that I regularly feel guilty about it.
I am tenured with A13.

You don't need to feel guilty :) as long as you are open about it and don't become arrogant towards others, any reasonable person will wish you well.
A13 gD or hD? In the latter case, there are still development opportunities.

We would need to borrow about €370k (for construction costs of 700k).

[...]

We could also borrow about €200k - 250k from our parents, which would be equally interest-bearing and therefore makes no difference.

If the money is really freely available from your parents, I would rather borrow it from them than from a bank. I would prefer to keep the interest within the family rather than giving it to a bank.
You can play around with it a bit. €200k from the parents, €170k from the bank. That also reduces the loan-to-value ratio and could lead to better conditions. You could keep the remaining €50k in reserve for unforeseen additional costs.
Or something like that...