How to become an English Expert? Can I focus mainly on grammar for now?

I want to become an expert of the English language. I’m currently studying English all day long. At the present moment, I’m studying basically grammar and I’m trying to do an accent reduction course on my own with videos on youtube, and I’m always improving my vocabulary. When I feel that I will have acquired as much knowledge as possible related to grammar then I will probably focus on other English skills. I don’t like to study many different things at the same time e.g. grammar, reading comprehension, listening comprehension, writing skills, literature, etc. I know grammar can slow your progress a little bit but that’s more related to basic and intermediate students, I think. So my question is, “Can I keep studying grammar for as long as I feel like it?” Thank you very much in advance.