Which task is worthwhile to do yourself?

If you have to take unpaid parental leave just to even lay floors, then you are no longer saving any money.

We thought about that too. Of course we can paint. And plaster. And stick vinyl. But we wanted it neat and fast. And we wanted someone to complain to if it doesn't turn out neatly. And we didn't want to keep arguing because of the stress. And whoever works (full-time) to pay for the house also needs a break. So we consciously decided NOT to do ANYTHING ourselves. Also unusual, I think all the neighbors here at least insulated their own roofs... never mind. What I do is the garden. I like it, and I can do it too. It's leisure and relaxation.

we do wooden floors, painting and as much as possible in the garden

I'm going to ask quite rudely in between:
how much value of own work did you calculate in the financing for [Außenanlagen Garten]?

I got a quote made just like for all trades.
Paving, fence, shrubs, and lawn. We included that accordingly. I would have to look up the total on the computer.
Ultimately, we will use it exactly for that, paving has been done, large shrubs I have done or help with. And the most important (and after paving the most expensive) is soil replacement and loosening here so that anything can be planted at all.
Since that can only be done with heavy equipment, I am not doing it myself.

If so, I would have proportionally calculated all labor costs from the quote and indicated it that way.

we do wooden floors, painting and as much as possible in the garden

now I'll ask quite rudely in between:
how much value of own work did you calculate for the financing of outdoor facilities garden?

Garden €3000 as the only own work item in the financing but only to get below 80% loan-to-value. Effectively only on paper because we are financing €20k for terrace, paths and driveway. Everything else like L-stones and terrain modeling with curbstones is included in the shell construction offer. Carport and foundation are included in the carpenter's offer.

Who decides whether parquet should be glued down? I need to educate myself.

In case of doubt, you do.

Don’t underestimate the time building will cost you, even without doing it yourself.

The only thing we planned to do ourselves was the wooden terrace because it doesn’t really matter if and when it gets finished (it’s still not finished).

I quickly gave up on the idea of painting myself. We would have definitely moved in about three months later if I had tried to paint on weekends. Painting isn’t even the most expensive trade; for example, it’s better if you install the underfloor heating and insulation yourself. But that might disrupt the schedule if you’re too slow, don’t have time, or make mistakes.

In the end, there were enough little things that we had to do ourselves out of necessity.

Usually, you can lay floors yourself well enough. Still, I was glad we had it done.

You save money more effectively through good planning, material selection, or purchasing yourself. But that also takes time and is only possible to a limited extent with a general contractor.