So, I'll begin by mentioning my (potential) credentials here; I was in the same boat as you - studied history in high school - majored in it in college, and am currently working as support staff for a University History Dept where I've gotten a good feeling on the internal academic process from both the university perspective and the student perspective (both through my own experiences and through discussions with our PhD students).

​

> What to study ? There's so much interesting and fascinating period I don't know which one to choose.

You don't need to decide now. Different universities and different countries have different beliefs in the degree that undergraduates have to specialize in. But generally, you'll have enough options to dive a little deeper into multiple areas that fascinate you. You do not have to enter college with the understanding that "I want to study british labor reform between 1920 and 1930." Take classes on the things you like, and if you decide you do want to be a historian, pick the subject that you feel like you can spend the next 7-10 years of your life learning about. It helps if you pick a topic that is underrepresented in the current market. For instance, in the U.S., there are wayyyyy too many Medievalists and Early U.S. Historians with not enough positions to really fill. Comparatively, subjects like Chinese and Japanese History is less bloated. This actually leads to the next thing.

​

> If there's some careers possible as a "general" historian that wouldn't be an expert on one subject but would be pretty good on various stuff.

​

Generally, this isn't the case. If you want a job directly in the field of history you're gonna need a PhD. The PhD process is demanding (see the 7 years before) and the very nature of PhD's means that you're going to be forced to specialize on one very narrow topic. For instance, lets say you like Roman History. Your thesis isn't going to be "Roman Politics between 20 BC and 0 AD" it's going to be closer to "How did Rome's diplomatic efforts with the Parthian Empire impact Augustus's ability to effectively reign." You're also going to have to write on a topic that hasn't been sufficiently written about since your thesis is supposed to contribute something new to the field, not just regurgitate old information.

Down the road you could become a "generalist" by discussing themes throughout history (The rise of capitalism in the west etc), but you're not so much being a generalist and instead becoming an expert on multiple topics and pulling it all together.

The other thing to consider here is that the job market for historians is abysmal. There are too many graduates and not enough jobs to go around. If you want to be a historian, you need to eat and sleep and breathe about your topic and you need to find a way to distinguish yourself from the pack. For instance, one of the job searches we ran recently had over 100 candidates. You have less than a 1% chance of being picked so you need to do everything in your power to do so. If you like learning about history, but the idea of diving into archives to try to find new research doesn't interest you, then it's not the field to pursue.

​

With that said, an undergraduate degree in history is incredibly enjoyable and can give you plenty of skills that can help you in the job market. I have no inclination to become a historian and I would do my degree again in a heartbeat. If you like history, you should pursue it. But just understand that your undergrad doesn't determine your job future, and if you do want to be an actual historian, you're going to have to put in A LOT of work over a very long period of time.