We as authors/writers string words together with the hopes that someone finds what we do appealing enough to spark their interest to the end... however, those sentences must be flawless. If they aren't, we authors/writers know it. If there are mispelled words, if there is poor grammar or poor punctuation, it trips up the reader...and if there are enough of them, the reader won't finish the book.
There are hundreds of sites that offer writing prompts and help with story beginings. There are also pay sites that offer the best in editing and publishing. As a writer, you NEED that second set of eyes...sometimes the third and fourth sets as well. We like to think what we write is flawless, but in reality, there are stupid mistakes we all make that we as the writer don't catch (even on the twelfth read-through.)
If you do not have an editor, proofreader, or beta readers--please consider finding one or all. It really helps when you have beta readers who love what you write. They are all about reading your manuscript before anyone else, and if you promise them a signed copy of the paperback, they will bend over backwards to help. There are hundreds of editing services and independent editors out there, including me. As my tagline says...achieving perfection one word at a time...is what we all strive for.
Challenge yourself to learn more about good grammar and composition by taking a class at a local community college, or one of the many courses offered online through YouTube videos. We are never too old to learn and when we develop the mentality that we are, we are sorely mistaken.
With pen in hand and/or fingers on keyboard...may your writing muse allow you to put down the words in sentence form that will be the most incredible, magical masterpiece you've written.