Oops forgot to check this for months my bad. I don't think I'm good at writing (lots of awkward sentence construction and unvaried vocabulary) but it just eventually got to this stage from playing games, reading books, and going on twitter. As for grammar guides I'm not the best person to ask, there are people around who know more resources than me (I just google stuff I don't know and eventually find it) and there are probably more "efficient" ways than ever to get a good grasp of grammar these days that I'm not familiar with.