Building ground suddenly a biotope

We signed with the company a long time ago and actually we should have accepted the last 2 price increases because it has taken too long from our contract signing to the start of construction for them to keep the old prices. But the boss said that it is not our fault and they have not had this case before, so the old prices remain in place for us. We also went through new floor plans once. Free of charge from them. And above, that is to the north, we would only be looking at a wall because the plot is so high. (To the south we can go out of the house and to the north we can almost jump onto the roof) Explaining this is extremely difficult because of the slope.

I have to briefly mention thanks again for the help. We planned the interior for about 2 years and went to numerous house viewings, so I'm also a bit stubborn about replanning because it is so optimal. Regarding the costs, we had initially calculated about 150,000 for a plot of land but got it for 50,000, hence the buffer. And I would rather be annoyed in 10 years about having forgotten an outlet than having placed the house incorrectly. We are 23 and 24 years old, so we can handle that well. I am really grateful for the help; I just don't want to regret having saved money on that in 10 years. We also currently live on this street and the house is built on the street.

Have you ever spoken personally with the nature conservation authority? Such a nutrient-poor meadow can be restored after the cellar has been built and the walls have been supported. It is best to discuss this directly with them. Where that is not possible, you might be able to offer compensation areas elsewhere.

If you work it out together with them using proper plans in front of them (your graphic work is unfortunately terrible - please have someone else do it), then you are more likely to get the decisive stamp on the building application. At least, that was the case for us.

The plans of the house and everything were made by the construction company. We chose one online, went to the company, told them how we wanted it, they made the plans, surveyed the plot, and sent us the construction plan. We only had to go to the neighbors to get their signatures. Since then, we only had to go to the tradespeople like electricians, etc., and choose the sockets, sinks, and things like that. We wanted to make an appointment immediately, but this request unfortunately went unanswered. So the plans are from the architects and the construction folder as well as the email correspondence come from the company or they rephrase the questions so that they fit.

I have to quickly mention thanks again for the help.
We planned the interior for about 2 years and went to numerous house viewings, so I am also a bit stubborn about redesigning because it is so optimal.

That is understandable. Of course, you don’t want to throw the planning overboard.
However, it’s about a lot of money. Just because your construction company waves a solution doesn’t mean you have to bite immediately.

Regarding the costs, we had originally calculated about 150,000 for a plot of land but got it for 50,000, hence the buffer. And I would rather be upset in 10 years about forgetting a power outlet than having positioned the house wrongly; we are 23 and 24 years old, so we can handle that well.

It’s nice when unexpectedly so much remains from the inheritance. No reason to just throw it away. With 50K €, you have many solution options that are worth trying out. It just seems to me that you are a bit overwhelmed and need help.
Find yourself a proper planner, put 5K € on the table so he can talk to the authorities.

No, we are not allowed to do that, the house must run parallel to the street on the longer side

A house must fit the plot and what is permitted. A slope is really no problem. On the contrary, this way you can access the garden from every level. Others pay a fortune for a rooftop garden just to be able to go outside after the sauna. If the slope is properly planned, you don’t look at a wall. You have to build with the slope.