Cool. Solved my problem.
Here comes another question in my mind.
Is there any snippet if I disable sidebar per category it will be disabled authomatically in all posts of that category so I should not go post per post to disable sidebar?
I want to disable sidebar in more than one category using snippet provided in this URL: https://docs.generatepress.com/article/sidebar-layout/#using-a-function
I see that sidebar is disabled in one category but not in all of them.
I also added three sniipets for three categories seperately but code snippet plugin did not accept more than one.
I have three categories and slugs are math, physics and chemistry and changed if ( is_category() ) to if ( is_category(‘math’,’physics’,’chemistry’) ) but it did not work for all of them.