The thing about writing dialogue in books and stories, is that you can't match it perfectly to real life; and if you think you do, you've gone horribly wrong somewhere. Think about it, in real life conversations, you can hear people talking over one another, interrupting each other, switching topics without warning. And kinda like in the way your thought process goes, ideas can overlap one another. In books, you're not trying to write a real life conversation, you're trying to give off the impression of one. Because if you try to replicate that real life dialogue, you're going to confuse your readers and you don't want that, you want the story to flow.

The other thing is that in writing, dialogue must have a purpose for it to interest the reader. Now, not saying that there has to be a conflict at every turn, that's going to make it sound like no one can get along, but sometimes, a simple exchange can just bore your readers. Give the dialogue a purpose. For example, give your readers information they couldn't find out another way, tell us a little bit more about your character's traits and such. Give it some reason to be there.

I think about dialogue a lot. I'm a theater kid. I'm always, constantly thinking about new monologue ideas, or maybe a scene I'd like to perform, and of course, dialogue is one of the most valuable and important parts of acting. But kinda like in acting, there's no way that you can get through a scene with real life dialogue. Dialogue needs to move the story along so that you're not constantly stuck in the same exact place the entire time, and it needs to be executed in a way that flows.

If your dialogue could be taken out of the scene without any changes or any information going with it, then it's worthless, and you can go ahead and get rid of it.

And please, PLEASE, get your punctuation correct. I understand that it's easy to mess that stuff up, but it needs to be said. Punctuation is a very important part of writing, and dialogue in your book.

Another thing to remember when writing dialogue is that you can't have all of your characters sounding the same. This mostly has to do with writing characters in itself, but dialogue is one of the important parts. You can't have every one of your characters be the sarcastic one, or the loud one, or the one who can't break out of their shell. Every character must be different and that goes hand in hand with their dialogue as well.