How quickly should one pay off a house?

Get a massage three times a week and do a self-paying psychotherapy.

Yes, yes – and always remember: people are different. I accept that your best idea of a vacation is Disneyland. Thousands of people run there every day. For us, it’s nothing.

It’s not "my best idea of a vacation."
But you know who would find it amazing? My daughter!
So it’s a guess. Maybe not. Then we’ll stop and go home. At least we tried and didn’t "categorically rule it out."
It was explicitly a spontaneous example of what we would do if we didn’t know what to spend money on. It was also explicitly mentioned that it would be done in addition to the proper vacation.

On the topic of finding ideas:
You say you have some friends.
What do they do besides going to the gym?
It’s a guy question. But I get really enthusiastic about friends’ hobbies quickly. I have at least 2-3 things in the pipeline that I’d like to do with some people. Unfortunately, mostly too little time. And my main hobby (mountain biking) already takes enough time and money...
Is there nothing besides beekeeping and potato farming?

I also don't quite understand why we should help you improve your quality of life. You yourself write that you lack nothing.

Maybe others here have experienced something similar. Much of it is simply luck that we were able to build at relatively low prices and secure favorable interest rates. Then inflation came and also devalued the remaining debt (salaries have risen sharply). Maybe others here are experiencing the same.

On the topic of idea generation:
You write that you have some friends.
What do they do, besides going to the gym?
It’s a guy question. But I really get enthusiastic quickly about friends’ hobbies. I have at least 2-3 things in the pipeline that I’d like to do together with some. Unfortunately mainly too little time. And my main hobby (mountain biking) already eats up enough time and money...
Is there nothing besides beekeeping and potato farming?

At least on weekdays they are in the routine of work/kids from morning till evening... and then they’re happy to watch an hour of Netflix in the evening.

We often meet at our place / at theirs or use the city’s offerings together, e.g., city park/zoo/etc... summer outdoor pool, Christmas twice a week Christmas markets, etc... no one does anything special there.

Some drive themselves crazy with stocks, stock picking, crypto, etc. – doing analyses and stuff. I have excluded that for myself. World-ETF and that’s it.

Teriyaki... I thank you... really. You are the best example of all time that you can sit on a big pile of coal and still be inwardly consumed, restless, unhappy, aimless, no idea what. You do EVERYTHING that the mainstream dictates to you... still unhappy... and you wonder why? That is really sad... especially for an apparently intelligent man in his mid-30s. If you were 70 or just dumb... ok. But like this?

Oh... Tips...
You say you live in a big city? Just go to the food bank on a nice sunny Saturday morning. There you will meet many people.
Ask them what you’re supposed to do with the 2,000 scoundrels a month, for whom you simply can’t find any use in your life...

Just under 2,000 EUR, that’s what a family of four in Germany receives as citizen’s money, plus rent. So they basically live on the money that you can’t manage to spend monthly because you don’t know what for...

I wish you a speedy recovery.