Constantinos Kalampokis’ answer to What is said at Greek funerals? covers everything that happens at a funeral; but I’m assuming the question is particularly after what the condolence formula is.
Both Greek and Turkish are notorious in linguistics for having a formulaic expression for just about every occasion; it’s part of good social behaviour that you’re expected to come up with the right formula for the right occasion. Hence the proverbial expression for someone tactless: Πάρ’ τονα στο γάμο σου να σου πει «και του χρόνου», “Take this guy to your wedding, and he’ll wish you ‘Many Happy Returns!’”
In funerals, the formulaic expression is ζωή σε λόγου σας “life to you” (where λόγου σας “your word” is an old circumlocution for “you”, cf. “your lordship”). https://www.translatum.gr/forum/… offers the alternatives ζωή σε σας “life to you”, and να ζήσετε/ζείτε να τον/τη θυμάστε “may you live/keep living, so that you can keep remembering him/her” (i.e. may his/her memory survive in you).
Τα συλλυπητήριά μου “my condolences” is a more formal, stiff expression; I doubt you’d use it with friends. Κουράγιο “(have) courage!” is also heard, to acknowledge the hardship of family members.
I have a lot of time for the expression Να είναι ελαφρύ το χώμα που θα τον σκεπάσει “may the soil that covers him be light”. But that’s not used at funerals, it’s a valediction typically used for famous people.