Go to Greece first and then Türkiye. What should I do with a visa?

These two countries have nothing to do with each other. You must arrange your itinerary before applying for a Greek visa. The Greek visa is a Schengen visa, which is more troublesome. The first time you apply for a Schengen visa, you are generally only given one validity period, and the entry date will be the same. Your itinerary is exactly the same.

The Turkish visa is now an electronic visa, which can be applied for online and can be issued in a few hours, which is more flexible.