This is the 6772nd most frequent Turkish word.
belediyesince
"Belediyesince" means "by the municipality" or "according to the municipality" in English.
In this sentence, 'belediyesince' means 'by the municipality' and indicates that the municipal authorities were responsible for the action of repairing the road.
Bu yol, belediyesince onarıldı.
This road was repaired by the municipality.
Here, 'belediyesince' again signifies the agency ('by the municipality') behind organizing the festival.
Festival belediyesince organize edildi.
The festival was organized by the municipality.
In this usage, 'belediyesince' is used to highlight the body ('the municipality') responsible for arranging the event.