
Make your manuscript the best it can be. Get a Professional Editor to conduct a Developmental Edit and provide a marked-up script, plot and character analysis and overall report. There are lots of tools that help you along with copy editing but only a Human Editor with experience can really do what you need.
https://www.offworldpublishing.com/jamwriterediting
As an editor and ghostwriter, I agree. Its very difficult to edit your own work, and getting someone else to help can give valuable insight to making the book better