Land purchase: What urgently needs to be considered? Tips?

Good evening everyone, we hope for strong support.

Background: My partner and I do not feel pressured to build a house or buy a plot of land. We wanted to use this "no pressure" and always calmly look at plots and strike only when we both have the WOW effect.

On 01.05.19 we inquired about a plot where we had already seen in the pictures oh... this could fit in terms of location and the land. We dutifully sent the inquiry and unfortunately received no answer.
This morning we spontaneously thought to call the real estate agent once and ask. She apologized and also told us exactly where the plot is located. She already mentioned that last week she was on the plot with another interested party.

We jumped into the car and drove to the plot... it happened as it had to... the WOW effect was there.

We called the real estate agent and told her that our feeling was good. She was happy but mentioned a call from the other interested party that he also expressed interest today on the phone.

We are meeting her alone tomorrow afternoon at the plot to speak personally.

On the way back we spoke with the bank. Financially, this is not the problem.

There is still a house on the plot that would have to be demolished.

The listing states the following:

The plot with the still standing garden house is very quiet, romantic and located at the end of a small access road. Nevertheless, you can reach all daily necessities in a few minutes and the highway on-ramp is only a few kilometers away.
The garden house is in need of renovation or demolition. Should you plan a new house, nothing stands in the way.

The garden house looks bigger than a garden house. It seems to be an old dilapidated residential house.

Whether the plot is serviced is not apparent from the listing, but a telephone connection seems to be available. Telekom was already able to say what internet we can get there.

Are there any open points that we should urgently clarify / ask tomorrow + do you have ideas how we can secure the plot?

Thank you very much

Ina & Philipp

Is there a development plan? If yes, does it allow what you want to build? What are the building boundaries? The infrastructure is not the problem, that can all be arranged. It would only be bad if you can’t build what you envision. What about contamination? How was the plot used before? Could the soil be contaminated? You won’t be able to get a soil report in such a short time. Ask the neighbors if there were problems with the soil during construction.