People use the word "shit" very often in common conversation, but usually among friends. It's not recommended to ever use in specific cases such as the workplace, your instructors, business/casual events. Among friends and colleagues that you feel comfortable saying this around, it's usually fine. It's like <<merde>> in a sense, but with some culturally different uses, and more relating to either "poop" or "stuff" in English. Hope this helps!

Depend of how the person use it because the word shit can be use in many different way.

People will use it casually, but it is normally considered to be offense.

shit is vulgar but is not offensive. exept if you ae calling someone a shit :D

It depends on who you're talking to. With friends or in a casual setting, no it's not a bad word. But others might find it offensive.