Kann mein Abo nicht anpassen, Feld i bei Bestätigung kann nicht ausgefüllt werden.

you may not be eligible for the discounted price.  that's often for first time subscribers only, so check the fine print. if it appears you are eligible:

use a browser that allows popups and cookies and contact adobe support by clicking here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
in the chat field (lower right), type AGENT
be patient, it can take quite a while to reach a human

p.s you can also use phone (but chat is usually quicker), https://helpx.adobe.com/contact/phone.html

p.p.s. you can also use twitter to tweet @AdobeCare

p.p.p.s. if you're contacted by anyone (via email or private message), it's much more likely to be a scammer than an adobe representative. ie, double check for an employee badge if contacted in the forums and look for an adobe.com domain in the email address if you click reply to an email. then check again and be very suspicious. any other method of contacting (or offering to contact you) is almost certainly a scam, https://community.adobe.com/t5/using-the-community-discussions/staying-safe-in-the-adobe-support-community/td-p/12919684/redirect_from_archived_page/true

Let me move this to the Account, Payment, & Plan forum for you, which is the appropriate forum for your question.

* The Using the Community forum is for help in using the Adobe Support Community forums, not for help with specific programs, installation issues, or account issues such as subscription questions or billing problems, or generalized questions about Creative Cloud services.
* Questions about business plans should be posted in Enterprise and Teams 
* Product questions should be posted in the associated product community.
* Installation questions should be posted in the Download & Install community.
* Account issues, including subscription questions or billing problems, should be posted in the Account, Payment, & Plan community.
* Questions about the Creative Cloud desktop app or general questions about apps in the Creative Cloud should be posted to the Creative Cloud Services community.