I've spent 40 years writing research reports and press releases, always wanting to write for fun. I've worked with professional editors and know what the best can do, and try to emulate that. Of course I look for grammar and typos, but its more important to look at logic, consistency, plausibility — basically anything that might take the reader out of the story. I won't tell you how to fix your story, that's your job. I will offer suggestions which you can use or not as you wish.