You should not avoid holidays. Rather, look upon them as an opportunity for special travel experiences.
Does Turkey close up tight for holidays? Not at all. You’ll have plenty to see and do, but good planning will be rewarded.
Banks, government offices and many large businesses close completely for national holidays, as do many shops, but most museums, archeological sites, national parks, etc. are open, and busier than normal.
As for religious holidays, it’s a bit more complicated. Islamic holidays follow the traditional Islamic Hijri lunar calendar, and are therefore celebrated about 11 days earlier in one year than they were in the last. They may begin and end on any day of the week.
On the first day of a multi-day religious holiday such as Ramazan Bayramı or Kurban Bayramı, just about everything will be closed, but some museums, restaurants, etc. may only close for the morning, and will open in the afternoon. Public transport will run on a special schedule, perhaps a Sunday schedule, or one unique to that holiday.
On subsequent days, most museums, galleries, historic sites, etc. may open, depending upon the particular institution, but they will adhere to their normal weekly closing dates. So if the first day of a holiday is Monday, Topkapı Palace Museum may be closed in the morning, then open Monday afternoon, but closed on Tuesdaybecause it is always closed on Tuesday, holiday or no holiday.
—by Tom Brosnahan