Fully financed property or pay in full

Doing everything yourself right away, like repairing a car, isn’t necessary, but I still inform myself beforehand about where the problem might be or what laying methods there are for terrace slabs. I just don’t trust the "pros," many work according to the motto "we've always done it this way, so it must be good" or something similar. But you have the rest, it’s quite similar to building a house. Either the all-inclusive package, where I have less effort but only get standard, or non-standard, but with more work.

Prime example workshop - one replaces 3 parts for €200 including labor and it runs again, the other replaces the entire engine and the problem is not solved.

I was annoyed with the car for so long until I decided to do almost everything myself. Now I have some knowledge and technical understanding.
With financial products, I have at most rudimentary knowledge. By the way, I have learned a lot here. However, for an investment, my knowledge and also my understanding of the capital market would not be sufficient. I also doubt that I can acquire the knowledge within an acceptable time frame. Therefore, I rely on a certified financial planner.
The same goes for trades in the house. I either acquire knowledge myself, if possible, or I take trustworthy contractors. Personally, I also feel ripped off way too much, badly advised, poorly done work. And given the background of the shortage of skilled workers, it will not get any better.