Grammar is not an easy topic for many people. So, I applaud you in your endeavor to get better.
When it comes to parts of speech, there are eight elements. Nouns, Verbs, Adjectives, Adverbs, Pronouns, Prepositions, Conjunctions, and Interjections. Once you master these or get familiar with them, you need to know how they function within a sentence.This is where you need to learn about the parts of a sentence, which are: subject, verb, indirect object, direct object, prepositional phrases, and clauses.
Finally, there are verbals: participles, gerunds, and infinitives. In a short post, I cannot go into detail on any of these topics, but I will link a grammar website for you. Go through it, and you will learn a lot.
As for the writing process, here are a few tips. First, read as much as you can. Second, practice writing. You cannot get better, unless you start writing. Write anything. You might want to use what you have read as a springboard. Finally, organize your thoughts before you begin.