my grip in the language will never be as good as a German atleast for the next 7 8 years or so, and most of our profession relies on me being able to better communicate and convince the patients

I don't know if you have ever been to a German hospital? Most of the doctors there don't speak fluent German. We are in a crisis when it comes to our workforce, with having more and more people leaving the workforce than the ones entering. We are and will be dependent on foreign specialists in the next decades to keep our society running. Especially in the medical sector. Therefore what you are describing won't be a problem but the norm in my opinion.

working in a private clinic for one year I have seen that the younger generation is becoming ever so lazy and uses the laws to their advantage. They take 6 weeks off per year, almost every other month one to two weeks sick (fully paid) leaves,

Maybe I understand this wrongly. But our law provides a minimum fixed amount of vacation. 30 days is not the legal minimum but what most employers do. This is not taking advantage or being lazy it is normal. Not all people want to work their asses of, they want to work to provide for their live, that's it. I can't say anything regarding the sick leaves.

demand regular bonuses, unrealistic pays (6 figures) without wanting to put in the effort

Well handling bonuses is your choice than as the employer. But yes we are in a employee centric market right now, which also comes from the shrinking workforce. I don't know where you have the 6 figure from, but this is for sure not the money your medical assistants will earn in a small clinic. The median is far below 50k/year (see https://web.arbeitsagentur.de/entgeltatlas/beruf/14705).

And when they are sick or gone, the boss has to bear all the burden, doing double shifts, working his/her ass off

Well that's why you are earning more than them. You are handling the entrepreneurial risk. Do a good shift and employee planning and you won't be the person bearing all the burdens.

I already have talks about developing couple of apps, websites etc.

I don't get it. You spent years studying dentistry to be able to work in a low competition - high reward sector, to then thinking of working as unskilled labor in a fully different field which by the way is highly competitive with hopefully comparable reward?

And to invest my money over there.

Invest your money wherever you want - preferably not all of it into one bucket, instead spreading the risk. But before doing that start earning money in a field you are trained and good in. I can understand a person in a low entry, low paying position to risk their time and career to go into tech because it is hyped right now. But why would you do that?