Financing the construction of a house on a plot of land based on the neighborhood

Sorry, if that were true, the realtor would have already passed the property on to the higher bidder.

I think this step also takes time. The bidder still needs at least 1 or 2 weeks to secure the financing. The broker leaves it open until he receives the money.

How large is the property?

the plot is 409 m2 (~ 21m * 19.5m)

the plot is 409 m2 (~ 21m * 19.5m)

Then draw it out and try to realize a townhouse there in the size or area proportions house/plot (neighboring development Par. 34). It certainly won't be easy. In the end, you will have to live with all the disadvantages that you probably have everywhere in tight spaces. At the same time, I would also look at comparable semi-detached houses: there are surely developer offers that are more manageable in financing and less risky.

the plot is 409 m2 (~ 21m * 19.5m)

It has nothing to do with the topic, but luckily I don't live in/near Munich, unbelievable these prices :D

1- How could I get an estimate of the fair value for such a plot? If it is really worth that number, I could offer more (2450-2500 EUR/m2).

Fair is a difficult term. The market regulates the prices but not who is allowed to participate. Given the low supply in the area and a distance of 15 km to the city center, the seller's demand seems quite realistic to me.

2- Is it really risky to buy a plot where the neighborhood is still under development? Could that really change significantly? Is it normal for banks to apply higher interest rates for such a plot? I find it very difficult to get a binding confirmation from the building authority, as it costs a lot of money and too much time.

I see no risk for the construction. You will see what is possible and what is not, this is done in consultation with the building authority. You can inquire with a house type that approximately matches your wishes whether it would be approvable. A binding commitment is only always granted with a building application. This form of preliminary inquiry would give me sufficient security. It is normal for banks to find reasons to raise interest rates. This includes an appraisal deviating from the market price.