I am of Turkish nationality and have a residence permit from Greece. If I fly from Turkey directly to Germany, do I need a visa?
No. Your residence permit from a Schengen country allows you to travel to other Schengen countries for up to 90 days in any 180-day period. See Travel Documents for non-EU Nationals:
If you have a valid residence permit from one of those Schengen countries, it is equivalent to a visa.