As I said general culture or general knowledge is described as below:
General knowledge is information that has been accumulated over time through various mediums. It excludes specialized learning that can only be obtained with extensive training and information confined to a single medium. General knowledge is an essential component of crystallized intelligence. It is strongly associated with general intelligence and with openness to experience.
Wikipedia

Longman Dictionary describes general knowledge as : knowledge of facts about many different subjects

So What would happen if you have a basic knowledge of many things and sciences and ... So you can decide better about everything of every day life.
There are many tests that can measure a mans general knowledge. The more you answer to the questions in those quizzes the more your general knowledge is.

I suggest that if you know the importance of general knowledge or general culture so try to read more books about everything.

These books can be about economy, geology, geography, history and even novels.

To estimate your general culture you can google it. There are many quizzes on the net like: https://latinamericanpost.com/29822-how-much-do-you-know-about-general-culture