Sure, there's a time and place to be a little more formal. You don't need to like, literally write how you talk, like, um, all the time. This especially won't work if your writing for character in the past, or if they're very different from you. Royals aren't going to "stay in and chill" tonight. Or if there's a profoundly important object, go ahead and give it a little more attention and description.
But don't dedicate too much description to ordinary things.
Sometimes I'll be looking at books on amazon, and the synopsis details a very complex plot, yet the book is less than 200 pages. Alright, great! This means they cut right to the action, right?
Yet when I read the preview, the story opens with a very detailed description. Like, the most important thing to know is how shiny, soft, and luminescent (I mean, really?) the character's hair or whatever is. Or, the details of the carvings on stone in a room we're never going to return to.
I didn't pick up this book for you to prove to me you know big words. You promised a good story. Tell it.
To these authors:
"It is my desire for you to cease your obnoxious activity."
Um. I mean, "I wish you would stop doing that."
I know it can feel weird, especially if you're still in school. English classes teach us to be a little more formal.
But now, you're writing for yourself (and if you're not, please ask yourself who exactly you're doing this for). You get to do whatever you like. Creating your own story is one of the most freeing experiences there is. Don't let yourself be held back.