Re: how do i remove my txt messages off the middle of my screen
It all depends on the message app you're using. I know the default Samsung Messages app will show a preview by default on the lock screen when you get a message, and other apps like Handcent SMS can show a popup as well.
The easiest way would be to download the Hangouts app and use that for SMS purposes, but you can also look in the settings for your particular Messaging app. There is a slight issue with Samsung's approach in particular though: While you can disable the preview of the message on the lockscreen (press the Menu button > Settings > More > Uncheck "Preview message"), it will still show a banner on the lock screen indicating you have a text.
The Hangouts app works quite well for both SMS & MMS, and is what I use myself.