Under 18 child with GV can he go to school in german as a non international student?

[wkb]

Portugal GV gives you residency in Portugal. To be a resident in another country, you need to apply for residency in the country you plan to live in. I believe Germany also has a golden visa program.
This thread discuss the maximum length of stay allowed in other EU countries.

Holder still subject to 90/180 rule for other EU countries?

Hello everyone, I am a US citizen and want to spend more time in Europe to get around the 90/180 rule (when the EU will allow Americans back in I started looking at a possibility of a Portuguese GV, but am not sure whether it gives me the right to spend time in other Schengen countries. For example, if I have the Portuguese GV, can I spend 4 months in Spain or Germany? Or am I still a subject to 90/180 rule? Any help is appreciated.