study Boris Spassky. he was a master of the closed Sicilian. You will learn much from his games to improve your play as black. because you can not avoid closed Sicilian positions as black.
what to do against closed sicilian
Most players consider the position after 1. e4 c5 2. Nc3 Nc6 3. g3 g6 4.Bg2 Bg7 5.d3 d6, the Closed Sicilian. The 2 main moves to consider are 3.Be3 and 3.f4. There are plenty of free resources like videos, databases and game collections that can help guide your decision.

the closed sicilian
He means which variation of the Closed gives you problems?
After 1.e4 c5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.d3 d6, you have:
6.f4 - A favorite of Spassky's
6.Be3 - I forget who the biggest proponent of this line was - Muchael Adams maybe?
6.Nh3 - Duncan Suttles's favorite line
6.Nge2 - another White option.
6.Nf3 - Counter-intuiative, but an option.
As black I've been experimenting with a quick b5 as in playing c5 Nc6, g6, Bg7 then immediately Rb8 and b5-b5. So far it's been good enough and different from usual stuff like the Botvinnik setup as black [which is solid but less exciting]. Bill

Watch Miodrag Perunovic’s video on the Closed Sicilian as Black on YT and never have problems again. The gist of the ~20 minute long video is essentially go c5 d6 g6 Bg7 Nc6 Nf6 Nd7 Rb8 b5 a5 b4 and play for the Dragon bishop and queenside counterplay. Of course, there are some mild variations depending on what White does (like going e6 Nge7 rather than Nf6 Nd7) or learning the Botvinnik setup against certain lines.

Another closed line against the Sicilian is the King's Indian Attack. Against that, as Black I would play a Botvinnik formation.
Another closed line against the Sicilian is the King's Indian Attack. Against that, as Black I would play a Botvinnik formation.
It is indeed a very solid setup vs closed! Before I starting using the early b5, my decision tree was
Nf3 before f4 => Botvinnik setup and
f4 before Nf3 => play e6, Ne and f5

I was gonna say "2. ... a6 is very good!" But then I read the original comment. Dont know what to say.

i consider closed sicilian not very good but u can just play the dragon line for white for any sicilian as it is solid and castle but it gets tough if u dont play d4 after d6 cuz b5 and then ur knight has to go to d2 but b5 is not good because it allows a3 which after you take you can just develop your knight and if they take you can take back and develop bishop on b2 (i wrote this as i sicilian playing 300 rated ik its not theory)
Carlsen called the Closed Sicilian 'something bad'
https://www.chessgames.com/perl/chessgame?gid=1766975
I'm a Sicilian player but I don't what to play against the closed Sicilian. I usually played a6 but I don't think it's to good.