If I understand correctly, your contract manufacturer is in Germany. All manufacturers of medical devices that want to be placed on the EU market (regardless of whether they are sold only in the home country or also in other EU countries) must be in compliance with MDR since May 2021.
If its medical devices are already certified according to the MDD and MDD certificate is valid for example until October 2023, this MDD certificate is still valid until October 2023. This means that the contract manufacturer must prepare technical documentation according to Annex II and Annex III to be in compliance with MDR until October 2023.
In the meantime, audits that will be conducted in 2021 and 2022 will require from contract manufacturer to prepare the following documents in compliance with MDR (Article 120):
Post-market surveillance system Vigilance system Mutual obligations with economic operators
If you are a contract manufacturer, you need to have implemented ISO 13485. The question here is who certified the medical device. If your marketer is responsible for the CE marking of the medical device, then there is supposed to be a Quality agreement between you and your marketer. In that agreement must be stated mutual responsibilities.
Template of that agreement you can find in our documentation toolkit on the following link:
Also, as contract manufacturer be ready that notify body for CE marking will audit your company as part of the marketer's audit. It means that the whole audit according to necessary requirements for production and additional services from ISO 13485 will be performed at your company.
There are no strict requirements that you need to be certified according to the ISO 13485, but your marketer as CE mark holder must be.