There is nothing like a "Terminal 1" at TXL, only Terminal A, Terminal C and Terminal D (and B and E, but you won't recognize them as discrete terminals).
Obviously you are flying into TXL on Aegean, they usually arrive around gate A6 or A7. Note that TXL does not have a concentrated baggage claim area in Terminal A, but single baggage carousels right if you enter the terminal building. KLM flights depart from Terminal D, i.e. you have to pick up your luggage at your arrival gate, carry it to Terminal D, which is about 400 meters, and check-in there at the KLM desk.
Given that the A3 flight is on time or not significantly late, 2 hours are fine.