It's a known fact that readers are turned off by typos and grammatical errors. It interrupts the flow of the story. You need a good editor and a good proofreader. The two are not the same. Your editor will make sure the story flows. They will help you flesh out your characters and organize your chapters. A good proofreader concerns him- or herself with every space, punctuation mark, letter, word, sentence, and fact in your book. They will make sure that nothing detracts from the information you are relaying.
A World of Proofing has 2 decades of experience behind it proofreading all forms of written media: blogs, essays, websites, presentations, cover letters, novels, novellas, short stories, series, dissertations, word games, screenplays, nonfiction... If you write it, we'll read it. We'll return to you a document free from distracting errors.
Don't let typos lessen the quality and validity of your work. Neither Grammarly nor Word will catch the mistake below. Use a good human proofreader.