Many people will say that reading about it in English is more accurate, or more complete, or more clear. The problem is though that often English explanations are very general, and cannot take into account the similarities and differences between the target English grammar and your first language. Some grammar explanations written in English will show common mistakes, but they can't possibly show all of them.
The other reason why it's important to read about grammar in your first language first is that it is the fastest way to get a basic understanding of the concept. Linguistic concepts vary significantly between cultures. For example in Chinese, they use the same conditional form regardless of the likelihood of the event.
First conditional: "If our football team can score one more goal, we will win."
Second conditional: "If I were you, I wouldn't buy that car."
Many Chinese learners of English use the first conditional for all conditionals. Clearly in the second sentence it is impossible that the speaker could become someone other than themselves. While they can produce the "past simple, would/could + infinitive" structure of the second conditional, they don't realise that the two conditionals are used in different situations. If they had read this information in Chinese the distinction would have been clear - that's assuming that the Chinese speakers who wrote the textbook understood this distinction themselves.
After you have got the basic idea in your first language, then you can read about the same grammar in English. This should refine or extend on the idea.