The writing and editing of peer-reviewed research is a specialist topic. Few other types of writing will let you get away with the otherwise archaic terms like “hence.” Moreover, the expected structure of a research paper is highly rigid.
Journal publishers have some really good material for learning how to write a research paper. These resources are good because they address exactly what the journals want. In addition, (unlike an essay writing service) they are completely free and ethical to use.
Elsevier has the Researcher Academy
IEEE has the IEEE Author Center (good for electrical engineering and computer science).
Springer has author and reviewer tutorials in English, Spanish, Portugese, and Mandarin.
Nature Research (the publisher of Nature) has Nature Masterclasses. These courses are not free, but there are some free samples.
In addition, the reputable editing company Edanz has the Edanz Learning lab, which includes a large amount of well-presented information about writing and publishing in both English and Japanese. Many resources in the Learning Lab are free.
Finally, for learning to write about heavily mathematical material, I recommend Donald Knuth’s Mathematical Writing. It is dense and wanders a fair bit, but addresses a lot of issues that no other style guide covers. It was a great help to me when I was learning to edit mathematics.
I hope this list gives you some good leads, and I wish you the best of luck writing your paper!