But I ask myself, is it really our task to ensure noise protection or is it rather the task of the noise polluter to provide noise protection?
The gas station is existing and thus approved, but your approaching new building is not. Keyword: protection of existing rights. The operation of the existing gas station must not be restricted by a new building that is approaching. If necessary, a look at the approval notice of the gas station operation might help you.
We acquired this plot as a building plot with the note that a single-family house or a multi-family house may be built there.
However, that does not exempt you from building and/or immission control law requirements.
No one said anything in advance, I did not expect that this gas station could ever become a problem
Whom did you ask? Obviously no one from the expert field, because in infill development in mixed-use areas like yours, traffic and commercial noise is not always a problem, but in absolutely every case it should be marked with big exclamation points on the agenda.
Before the sale of the property, the former owner inquired with the municipality whether there could be any problems that the buyer should know about, and they said that no impairments were to be expected, that is what annoys me so much.
Is that in writing? Or just an oral report from the seller? Why even the seller without obvious development interest and not you as the future property owner and builder?