Cloud-Speicher nicht vollständig nutzbar

you'll need to contact adobe support to fix that.  but before you do, check the adobe photography plans (and click compare).  they are both less expensive and give you a lot more for your money than the lightroom plan you have, https://creative.adobe.com/plans

if you decide, you'd rather have one of the photography plans, when you contact adobe support to iron out the storage issue, let them know you want to swap plans and have them fix the storage so you can have the storage from both your mobile and new plan, or if you opt to keep your current lightroom, just ask them if they can fix the storage problem.

there are 3 ways to contact adobe; chat, phone and twitter:

chat:
use a browser that allows popups and cookies, and click 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.

phone:
https://helpx.adobe.com/contact/phone.html

twitter:
tweet @AdobeCare

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