I often see English sentences written in a fancy way with commas, for example, "At age 80, the greatest Maya king, Pacal dies." I would write " The greatest Maya king Pacal dies at the age of 80." Because this is the only sentence structure I know: Subject + verb + " at the age of 80".
This is just a simple example as I don't know where to pull complex sentences from which I see a lot in academic journals. As English is not my native, and at the same time, I am learning to write like a professional academic, I oftentimes feel uncomfortable and shakey to write complicated sentences, simply because I don't know what possible sentence structures there are and the rules.
What are the most used sentence structures, and if possible, what are the best resources I should study? I want to be able to justify every sentence structure I use and be confident with it. I would like to solve this problem once and for all.