Register a business for Twitch?

Do I have to register a business as soon as I make money on Twitch? (As an affiliate)

Yes you have to, otherwise you won't be able to earn any money.

You have to do this from the point at which you have an intention to make a profit. If you are already making money, you are already behind on the obligation.

In short: yes

As a minor, however, this is not even possible and requires a representative or the approval of a family court.

@Limearts got it right here.
As soon as the intention is there, you have to register a trade. It is enough if you offer a donation button. As an affiliate / partner you have to do it one way or the other. Limearts has already said everything else.

Of course, you also have to report every income and expenditure to the tax office.