Depression after notarized contract - experiences

Was I too optimistic?

Nope, just stubborn like a tank. For myself, I keep reading over and over: Money / Interest / Me / Myself / and more money and MY fear and MY worries, only to start with money calculations again. I mostly read worries about "Your" money and your condition; the others (family!!!) apparently just have to endure it the way you eventually decide. I've already said, if you're not careful, it might happen that you someday long back for these little worries of now; then crying and what-ifs won't help anymore. You've received a thousand pieces of information here; even more won't solve your problem. Your wife should know and urgently realize that YOU have this problem but in the end, she will have to deal with it too. But I'm sure the next calculation is already in the pipeline........

Total: €3,386 compared to income of €5,619

That's fine. More than €2,000 remain for food, vacation, and consumption. Asked the other way around: How much money do you lack per month?

Uff, so you bear the entire financial burden and yet she is listed as the owner?
Sorry, but I find the whole setup where your wife doesn’t take care of the finances at all very strange and it would be very costly for you in the event of a possible divorce (yeah yeah, that only happens to others anyway..).

It would be costly for him?

She gives up her own career to take care of his children, pays high taxes on her already lower income due to the care work she does for him so that he has a higher net income (in his separate account…), will hardly have any opportunity to establish herself professionally after the divorce (after all, she will have been out of work for years due to caregiving duties and will probably have to take care of his children "full-time" even after the divorce), builds hardly any own pension, so she will end up in old-age poverty – and you think it would be costly for him? I don’t think so.

Vacation, food, consumption, clothing, leisure, SAVING (without special repayments, the remaining debt after 20 years is 400,000 euros). I am forced to invest in an ETF quite soon, no other way possible.

When I read the other posts here, my financing seems like a harakiri action with a remarkably good interest rate :O

you are so right. That's why the thought too maybe: "Am I pushing my wife into something because I always wanted a house?"

And what is the house still worth after 20 years?

The outstanding debt is currently massively above the market value, otherwise the bank would not agree to it.