Stuttgart to Ankara is about 2,103 km and usually takes around 3h 30m in the air. The track it follows runs over Central Europe, the Alps, the Balkans, the Black Sea, and the Anatolian plateau.
Air lifting over the Alps and the Anatolian plateau can raise brief, light ripples at cruise; crews know these spots well and the movement stays gentle. Over the Black Sea, Central Europe, and the Balkans the air is usually calm and settled. This track threads jet-stream latitudes, so in winter you may feel a few minutes of light, choppy air high up; summer usually rides calmer.
For most of a flight this length you are at a steady cruise above the weather, where the ride is smooth; the livelier moments, if any, are short.