I write basically everything from mysteries to fantasy to romance to poems about socks. No, I have never been in a mystery, murder, or investigation, but the lack of experience will not stop me from writing about it. A big part of rewriting is research, surprisingly. One goal for most writers is to make the readers believe that, yes, this story is true and everything in it is possible. To do that, at least some aspects have to be realistic. No, a regular man cannot jump from building to building and shoot webs from his wrists. But, if you have him be bitten by a spider and given superpowers, then anything is possible and believable. Fiction is about writing the unordinary and extraordinary and making it seem like it could happen to anyone. It is about letting readers, for just a moment, feel like anything is possible. Words can leave us tangled in magic and hoping for something better. They can break us down and make us question the big questions. And when words come together to from sentences and sentences form paragraphs, paragraphs form chapters, and chapters form a story, then anything is possible. The reader's mind is yours to take away and meddle with until they read the last word. As a writer, you have the power to implant new ideas, make people really question right and wrong and how society works. A few words can change a nation. Such as "I have a dream..." "Four-score and seven years ago..." or "Mr. and Mrs. Dursley ,of number four, Privet Drive, were proud to say they were perfectly normal, thank you very much." even "That's one small step for man; one giant leap for mankind".
Words have power. Choose them wisely.
Don't be afraid to write what you will never know.