Hi Friedrich,

I'm a Python developer and I too have noticed how incomplete their documentation is.
No tutorials whatsoever in other places on the internet. No 3rd party tutorials :)
I spoke to Odoo partners and they have different prices to teach you Odoo16,
Cyberbros have an advanced course for 1599 USD, which contains 1 2 1 conversation with their programmer throughout the course and allows for flexibility and custom curriculum.

This forum is the most working Odoo forum on inet at this point of time.

You can call partners yourself (try the ones from India, cause they are available all the time for a chat (on whatsapp) )
and just ask them for custom training (per hour) if you have questions. They usually charge from 13USD for 15mins or about 30 USD per hour, so it really depends on the partner.
And don't forget to share here if you find better options to learn oddo too ;)