Create login.txt:
machine soap.domain-bestellsystem.de
login <username>
password <password>
Make sure to make this file only readable for root:
sudo chmod 0400 ./login.txt
Run Certbot in manual mode:
sudo certbot certonly --manual --preferred-challenges dns --manual-auth-hook ./auth-hook.sh --manual-cleanup-hook ./cleanup-hook.sh -d example.com -d *.example.com
This will generate a wildcard certificate for your domain without the need to manually enter the TXT records.