Blog articles language, English vs Local

Hey guys, I'm new to this site and I wanna know your opinion about what language to use in a new blog. I will start one in the direction of psychology and how to and I'm uncertain if I should start one on a global basis, or keeping it local (german). I aim at 20-30 aged for the "how to" part and any age for the psychology part.
My business strategy is to provide content, stack up readers, staying authentic and trying to connect with them and eventually create income via selling ebooks, maybe set up premium memberships (access to more specific content and guides) and depending on the traffic something in that direction too, don't know much about it though.


Advantages Local language:
- overall smaller project, more quality based, thus easier and quicker to do
- less competition
- probably closer relationship to readers
- better option to connect with people (being able to set up meetups)

Advantages Global language:
- overall bigger project with more opportunities, quantity and quality based, long term
- way more readers
- ability to cooperate with similiar writers/entrepreneurs
- easier to become a flashpacker, i.e. leveraging mobility, cost differences
- opportunity to engage readers in new projects


What do you think about my business idea?
Are my estimations about the advantages of both correct?
Which one should I choose regarding my idea of money making?

Feel free to correct / inform me about anything mentioned above.