This Hamza Baba grave is close to a mosque from 1960, but I think he lived much earlier. The text translates as: Hamza Baba (Hamza Father)
One of the Conquerors of Kirklareli
A.D.1361, Islamic Calendar 785, Roman 789
Read a prayer to his soul (fatiha prayer)
Mosque Construction Association 1960
[Thanks, Cihangir]