I want to ask if it is good to study openings by myself with engine and database.
I am rated 2140 on lichess.
In opening courses, the instructor tells you a move to play and maybe you want to play another.
So preparing by myself I think is better. What do you think?
Study by yourself but a good book is great help. I am studying the Benoni and in 2017 GM Marian Petrov publish about it in Grandmaster Repertoire (Quality Chess).
Before buying it I look for other options and in 2020 a FM published for Everyman Chess a book about the Benoni. He said he checked Petrov's book among other sources and his book was awesome because represented the ultimate theory about the opening, and refutes many previous literature.
Which you think I bought, the 2017 book or the 2020 one? The 2017 of course because a GMs has much knowledge and experience and he offers ideas. From a certain line he explains the pros and cons and even he offers different altertnatives so you can choose according your style. I guess that the last of the last by FM is just get the lines of others and overwrite with a very strong engine the theory written by others.