Is my company toxic, or is it the normal culture of working?

I joined a company (agency actually) in Noida as a Digital Marketing Intern. Although the official workweek is five days, tasks from upper management often spill over to Saturdays. This might be a typical agency culture, or perhaps it's a sign of a toxic work environment. My official working hours are from 10:00 am. to 7:00 pm, but I frequently end up working late to meet deadlines. Also I do daily up down hope more than 4 hrs.