Building land in the middle of nowhere with the house prices?!

The building area is relatively inexpensive

Exactly, and that is also reflected in the resale value. Why should you get big city prices when you only have to pay the land price for a rural property? The next buyer will also only pay the land price.

That sounds a bit different now than in the first post.

I think so too.

Personally, I find commuting by train rather relaxed, as long as you don't have to change trains too often.

I actually only see the problem that the OP has never really had to leave their comfort zone. But sooner or later, everyone who wants to change will have to grow wings.
It's interesting how things change in a forum with the users: I can still remember that more flexibility was advised, at least regarding the land search and the radius in which one should look when wanting to build.
If you are really not the type for a single-family house with a little garden at the expense of the vibrancy and options of a big city, then that's how it is. But the OP has to decide that for themselves, without tunnel vision.

Even just one restaurant and only one pharmacy is only one more than none at all.

Where there is a primary school and train connection, there will also be more than just a pharmacy and a restaurant. Apparently, the OP just does not know this yet, because the place has not really been taken into account.

One commutes 50 minutes, the other 15 minutes. Both work a lot from home. That works with 2 children - mostly.

In my opinion, both commuting long distances is not feasible. That can also cause trouble within the family itself.

I always look enviously at cheap land prices (while ours are close to 1,000.-), but then I always tell myself that there is a reason for low prices ...

Exactly, and this is also reflected in the resale value. Why should you get big city prices when you only have to pay land prices for a rural property? The next buyer will also only pay land prices.

I am aware that the land does not significantly increase in value. But the question I ask myself is: How does the house price develop on cheap land? What I mean is: how stable in value does the house remain when the location is poor? Will I still be able to sell a 500,000 euro house in a few years for 500,000 euros if things get tough, or will it be more around 400,000? Of course, no one can know that, but I think the land plays a crucial role in this. An expensive house therefore actually makes little sense. But at the moment, one already pays around 350,000 euros for a 130 sqm house (pure construction costs).

That depends on so many factors that it is impossible to predict something like that. How will the region develop economically? Will the pharmacy and restaurant possibly give up at some point because it is no longer profitable or they cannot find a successor? How will public transport develop? How will mobility develop in general? How will it evolve with home office in the coming years?

In Magdeburg, people also thought for a long time that this was the problem, not even an ICE stops here. If Intel really manages to pull it off now, this will be the chip boomtown par excellence... if it still falls through, on the other hand, it will remain the valley of tears economically...

But with all your many concerns, you should leave it. If you are already thinking about whether you will be able to sell the place again... I built my house because I want to live here. Selling should not even enter the mind...

Of course, no one can know that,

Exactly. Just as little as a property with very good infrastructure in a big city could lose value if a new bypass or unpleasant commercial establishment is set up next door.
However, 5 to 10 years should be manageable to foresee. What happens in 30 years probably doesn’t matter anymore. In the end, you build your house to live in, not to speculate.

I believe the resale value is a step too far for you. The question is whether you can and want to live in the countryside? - Try commuting too and take the train at those times. I once found it relaxing and pleasant. Now I don’t want to do it anymore - Children. I know both city and countryside. I see no advantages for children in the city. Depending on the village, you don’t actually need that much parental taxi service. Unfortunately, you often don’t get that through social media, but only through the village grapevine. Here, the parents are partly quite well connected and sometimes the children are at another family’s place after daycare, and then you drive them to dance classes, etc. The wind instrument association offers almost the same programs as the public music school, English for children, children’s gymnastics, riding, singing etc. everything revolves around the church tower. With that comes a lot of freedom. - The delivery service consists of pizza and you have to pick up the doner kebab. There isn’t much more culinary-wise. That was very hard for me at the beginning. Instead of falafel and dim sum, at the festivals there’s steak with onions, bratwurst and fries. Instead of after-work cocktails, there’s beer at the fence. Take a look at last year’s regional newspaper. You should be able to do it online in one evening. There you’ll find out a lot. Whether the train station is to be closed, if new school/daycare/after-school care is being built, revitalization, arrivals and departures, etc. Through volunteering you get connected quite quickly.