Answers
Fοllowing the existing legislation, family members of a Greek citizen who are entitled to Greek resident permits are: the spouse; the partner with whom the Greek citizen has entered into a cohabitation agreement if this was drawn up in Greece or before a Greek consular authority.
So you can take your residence permit as a family member of a Greek citizen if either you will be married or enter into a cohabitation agreement with your girlfriend as above.
There is no provision for getting citizenship due to a boyfriend-girlfriend relationship. In case you get married, you will have the opportunity to look into the options for getting Greek citizenship.
You can apply for a resident permit if you sign a cohabitation agreement or get married with your girlfriend.
Sign a cohabitation agreement with your Greek girlfriend when you come to Greece and then use it at your application for a Greek resident permit.
You can get a residence either if you get married to her, or if you sign a notarized contract that you are living together as a couple, which has the same legal consequences with the marriage.
