Grammar constitutes the whole structure and system of a language. If you are learning a new language, it is not possible to speak and write without knowing the structure and system of that language. One thing is certain, it is the fact that you cannot learn English without studying grammar.
Stage in Grammar Learning
Trying to run without crawling is also harmful when learning grammar. In foreign language education, including English, gradualism is essential, so it is a fatal mistake to try to move from one stage to another without finishing, to try to learn all the subjects quickly with an excessive ambition to learn, to mix up exercises to improve skills. This also applies to grammar.
Choosing the right resources
You need the right resources when studying grammar at your level. While you don't need to study the same topics over and over from dozens of different sources, you should make sure that you really understand a topic you're studying from a good print or online source. For example, once you feel that you have studied and understood the subject of "plurals" well from a good source, there is no need to study the same subject over and over again from several other sources. The key point in this matter is whether you understand the subject or not. If you think you don't understand, you need to study again.