There’s [LycaMobile](https://www.lycamobile.de/en/) with 20GB and unlimited calls for 4.99 euros. Ends on the 31st of March.
[Lebara](https://www.lebara.de/en/prepaid.html) offers 12GB and 50 minutes to 50 countries and Allnet-Germany and SMS-flat (this isn’t translated on the website, sorry!) for 9.99 euros. Ends on 4th of April.
Sharing, because I occassionally see posts seeking cheap options and this is what I found myself.
New customer only and Lebara’s says bonus Internet is forever. Lyca’s website doesn’t specify if it’s limited time only so I assume indefinite for any customer who gets it.
Enjoy. 🙂