I'm finding my writing isn't coming out how I imagine the scene in my head. I have a hard time of putting it into words that describe and illustrate it the way I want it to be. As a result I'm conforming to stereotypes and exceptionally uninteresting story lines and introductions to new characters and
Maybe you're looking at it the wrong way. Have you tried thinking about things realistically? Like, if this thing happened how would this other thing react and what would come of that.
Also it looks like you got cut off there and it would be easier to help if you had examples
I know you probably forgot about this question and that you asked it a while ago but something I remember hearing is that your writing sounds boring and predictable and uninteresting because YOU wrote it. YOU already know what's gonna happen. someone who's never read your writing before on the other hand, might not find it predictable. id suggest having someone beta-read it for stereotypes and such.
If the problem is more of a thing where you don't feel like you have the skills to pull off what your imagining, i'd suggest you write all your other scenes first, or even a different, more manageable story for a while. Sometimes you need to give your talent time to catch up to your dreams. Developing skill takes time, and sometimes that's what you need to be able to write the story you want to write.
hope I was at least sort of helpful. Good luck in your writing!