This is a technical support forum so I am not sure how much editing help you will get.
A few thing that have worked for me.
Copy a Post into a word processing program and run spell check - some programs also do grammar - make font size easy to read and double space - just read what you have written several times - read your Post out loud - hearing the words seems to help.
When you paste the corrected text in use the Paste Plain Text so you don't have formatting surprises.
If you are in school or college see if they have a short writing or journalism class you can take. If you are in school sometimes an instructor or lab assistant will help a stranger that wanders into their office. Some colleges have evening or extension classes that are not too expensive and maybe there is a class in composition.
Any of your friends had a journalism class or are literature majors? Some engineering schools also require tech report writing. Buy a lunch for a friend that has writing experience. (warn them you want help with a short story)
You are writing about .a subject you like - that helps a lot.