Hi welcome to the Community, you can enter into same sex partnership in Greece or Marry In Germany.
Greece haven't signed Same sex marriage yet. but civil partnerships is legal there which havealmost the same rights as Marriage, or you can also decides to travel to Germany and apply for Same sex Marriage since you have Greek Residence Permits and Travel Documents which allows you to Travel Freely in the Eu and reside in an Eu Country for a period of 3 months.
Same sex marriage became legal in Germany on 1 October 2017. A bill for legalisation passed the Bundestag on 30 June 2017 and the Bundesrat on 7 July. It was signed into law on 20 July by President Frank-Walter Steinmeier and published in the Federal Law Gazette on 28 July 2017.
Previously, from 2001 until 2017, registered life partnerships (Eingetragene Lebenspartnerschaft) had been available for same-sex couples. The benefits granted by these partnerships were gradually extended by the Federal Constitutional Court (Bundesverfassungsgericht) throughout several rulings until they provided for most but not all of the rights of marriage.
For marriage in Germany and Greece you will need the following documents
Ehefähigkeitszeugnis, (Certificate of no impediment) also called Bachelorhood Certificate or Single status Certificate. This are Certificates stating that you can contract marriage and that you aren't in any marriage yet.
Your Original Birth Certificate
If any of you have been married before your Divorce degree Certificate.
Other Documents might be required from you depending on your Nationality and they might decide to send the Documents to your home country to confirm your identity and the authentications of your documents. try to be updated with the Registry office you are getting married in case they might require other documents from you. Good luck