I write using Word 2010, yes, old, but free. My first edit is just using the free self-checker that automatically attaches itself to Word when you write a story. Once happy, I then use the free copy of Grammarly, though Word and Grammarly often argue over commas and semicolons.
Once happy, I will have my story read to me by the computer, normally at 1.25x speed, as I find that amplifies grammatical errors. This is the biggest tip I can give to any author here. Don't rely on what you read with your own eyes. Let a computer read what you actually have written.
Finally, I forked out for Quillbot, which is okay, but take what it says with a pinch of salt, as it has a habit of wanting to suggest American grammar and spelling, even though I have mine set to British grammar. Note: all 3 programmes often have different ideas on grammar, and it often comes down to your own feeling.
Lastly, I have the computer read my story to me. Then edit when necessary, and repeat.
I will only hit the submit button when I feel it should pass grammar moderation. 😊