First thing first, this is a hostless event. it means that you will be all by yourself. You might find it strange but bear with me.
Long awaited Bienale just started.
https://bienal.iksv.org/en
it is one of the most prestigious art event in the world. Parallel to Biennale, many art galleries of Istanbul open amazing exhibitions.
Bienale will finish on mid November.
Some of the galleries which have exhibitions.
Salt Beyoglu
Galeri Nev
The Pill
Anna Laudel
Zilbermann
Dirimart
Arter
Galerist
ArtOn
X-ist
Casa Botter
Feshane Artistanbul