Assessing the affordability of home construction and criticism

It is foreseeable. It is now or in 3 years, but what fundamentally changes?

Aside from that, there are still 5k/net every 6 months as a bonus up for grabs.

Again, because you probably didn’t read it:
There are two critical points:
The bank doesn’t care about bonuses and the future. What counts are the last three monthly salaries and no probation period anymore. What happens later doesn’t matter.
Your wife is here in training without a visa, so probably doesn’t even count.
You are basically sitting there as the sole earner with a debt load of 700€. Ok, it’s land. But as long as that’s not paid off, it can also be a burden regarding your financing, because there’s hardly any bank that allows going into second charge with over 400,000.
Point 2: lack of equity to buffer, possibly to acquire something in [EL] or to work on it, to keep the calculation lean. The mentioned 11,000 are barely enough for kitchen, etc. But what if commitment interest comes up, a double burden due to default, etc…
Perhaps your “bonuses up for grabs” could apply - but honestly: if I say something is up for grabs, I can’t rely on it with certainty and calculate it in. You have too many ifs and buts in your calculation… that you yourself don’t feel secure there, I do not.

Just saving €1000. You really have to think about who can still afford a house if that’s not enough. And that despite €1200/month expenses for apartment and land.

Besides, there is still €5k/net every 6 months as a bonus on the table.

You have to remember that you’re building in the middle of nowhere. Land for €75,000 is insanely cheap. Elsewhere you’re looking at €200,000, €300,000, and €400,000 just for the land. The saving rates have to be higher, and so do the incomes – without dual income or a lot of equity it just doesn’t work. Probably the case with you too. You have all the cards in your hand but haven’t reached the crucial point yet.

The bonus doesn’t matter to the bank at first, but your probation period does. Of course the extra money helps, but it doesn’t change the initial situation. Better pay off the land in 24 months, marry your girlfriend, and use splitting to build even more equity. You’re currently paying €500 for housing and want to go up to €2200 for housing. That’s no small thing..

Just saving 1000€. You really have to wonder who can still afford a house if that's not enough. And that despite 1200€ expenses per month for apartment and land.

Apart from that, there is still 5k/net every 6 months as a bonus.

We save 2,750€ every month and have headaches about taking out a half a million euro loan. And if someone wants to give up other comforts for a luxury good (house), that is their decision. We do not want to change our standard of living because of a house.

You have to remember that you are building in the middle of nowhere. A plot for 75,000 is insanely cheap. Elsewhere, you're at 200,000, 300,000 and 400,000 just for the land.

I also like to generalize sometimes, but maybe it's a municipal plot at a Boris-price that would go for 150k€ on the private market, or there's still some contamination on it. That doesn't mean the bank calculates with a market price, but I wouldn't conclude directly that it's in the middle of nowhere.

I can understand that you want to build right away. However, I would also advise you to wait a little longer.
First, pay off the property completely and at the same time try to build up more equity.
The income should also increase in the coming years through your girlfriend. Until then, make sure that she is allowed to stay here permanently.
And then you should be able to get a loan for a house together.
By then you will have more equity as a buffer. Because building usually costs more than planned. Even if the house is planned to be turnkey with a fixed price.

And no one knows what will happen to construction prices in the coming years. At the moment, material prices have increased significantly, probably also due to Corona. Whether the prices will go back down is questionable. However, I also don’t necessarily believe that prices will continue to rise so sharply. But who knows.

Putting the financial situation completely aside, I would also wait. I myself am married to an EU foreigner (although from the other side of the world, the USA) and know about the stress with residence, visa, etc. A marriage makes many things easier, believe me.

I would wait a little longer, continue paying off the land (great that you already have one!) and then, when everything is settled and it is reasonably certain that you will stay together with your sweetheart, walk down the aisle and build the house. The children's school enrollment celebration then in the new and financially solidly planned house :-)