Taking pictures.

Nowaday taking photos has become a very common hobby.

I started when I was a boy and although I had not acquired high technical skills, I have not been not far from doing it professionally.
They are a lot of different activities: portrait, reportage of events, landscape, macro photography. It is difficult to name them all. I'm not sure what you mean in this sentence. There are a lot of different activities to photograph? There are many ways to take pictures, perhaps?
I think most of the amateurs just want a way to remember people and good times. For that matter photos are powerful tools. I wouldn't have been able to recognize some people if I had did not occasionally see them on photos I had shouted had shot. I also enjoy watching again some beautiful landscapes or happy events from the past.

As a hobbyist who wants to make some interessant interesting pictures, I think I have done a lot of errors. One of them was to persist trying to copy trying to copy some good pictures made by a professional photographers. Of course you can become very good at it and if you find pleasure in it then why not? It is interesting to try.
As an amateur you can should ask yourself who should would use your photos. This is the beginning of professionalism.

So far , I haven't done such a work.
So what study should I make what should I study before starting shooting to shoot?
What questions should I try to answer?

This is a list of possible questions:

-- Do I want to publish? (it is very easy to do it which is easy to do with the internet)
-- Do I want to sell the photos? 
-- Who is likely to use or buy my photos? 
-- What kind of photos I am am I able to do or what kind I have to learn to what should I learn?
-- What time will I spend for each project.
I don't think it is always good to ask myself such questions, but it is good to do it sometimes.

On the internet I have noticed that an image can be good when having a it is small size and can be bad when big but the contrary is also true (What is the idea you want to express in this sentence?). Some pictures need special care, but today it has become more easy thank's thanks to the computer algorithms. I mean: in the old times you could not have gotten a good result without the help of a professional photo lab.

You don't always get what you see all the time. You can even be amazed ? to get a good picture. I think, it is that's one of the reason explaining why it is so difficult to be a good professional: you must have a good enough experience and you must have learned from it. Some body Somebody might also teach you.

I restarted lately to make photos recently started taking photos again and I choose to take pictures of places I visit the most: the coast and around my town. But should I only think to take something beautiful? What would be interesting to shoot and whom for?

You did a very nice job with this interesting entry. It takes courage to deal with such complicated tenses, and you did it well. Good luck with your studies and your photography career!