planned house near a railway line

I would weigh how much train traffic there is there and take it into account. But I also think that you will not achieve the 500-600 in a sale. Every willing buyer will also want to negotiate the price down.

That is always difficult and the decision is up to you and will not be easy.

Humans are creatures of habit, meaning one gets used to certain circumstances, certainly with limits.
There is the nice anecdote where someone was asked if it bothers him to live by the highway.

Currently, we also live by two railway lines, S-Bahn and train. You can hear all the trains (old windows), but the freight traffic is a different category. The glasses in the display cabinet shake. However, the railway line runs about 5 meters below.
It was important to us that the bedroom faces the other side when sleeping at night with the window open.

Otherwise, the question about compensation is quite easy to answer. Which was there first? The railway line or your "house" or the plan for the building area?
It is rumored that this was among other things the reason why noise protection was built (or had to be built) for kilometers along meadows and forests at the A2. It was simply designated as theoretical building land, then the federal government had to pay. If it had later been found that something was to be built there, it would have been the landowner or municipality.

By the way, we have been living like this for 14 years. However, there is a difference between renting and building your own house there.

Just sit on the property on different days. Some things can certainly be considered in the architecture. Something can also be done with planting and vegetation. So it does not have to be a wall to have peace.

Oh, the train isn't that bad, it doesn't run every 10 minutes. And a sale is out of the question. But it could have been that someone here had the same situation as me. I just find it outrageous that the railway slapped up a wall in the new development area and the "older" developments get nothing at all.

That will have been regulated by the city (municipality), otherwise they would certainly have problems with the sale of the plots. Maybe there is a possibility through the city for the railway to accommodate you.

I strongly assume that it was not the railway company that built the noise barrier, but the city or the developer who erected it.

The reason is that for new building projects, the current noise protection regulations must be complied with; meaning without the wall, the city or developer would not have been allowed to build a single house there.

Whether this creates a claim for one's own construction project would have to be clarified by a lawyer.

You now want to build new yourself. Has your planner already checked your project against the current noise protection regulations? So are really just better windows enough?

I know someone who was only allowed to install non-opening windows on the noise side on the first floor, for example.

I don't know how much a wall costs, but even reaching one is not an option?