Site changes on a Small Screen

My site looks fine when the screen is large enough. However, when I size down my screen or view the site on a mobile device or ipad, I am not happy with how it looks . I am fine with it looking different, however I don’t want the menu to be a dropdown, and the phone number needs to be on the page, not way off surrounded by black. I am new at this, so is there code I need to add, or just a setting that needs to be changed? I am using DeCente theme.

Here is my website: http://biz104.inmotionhosting.com/~ftaggr5/

Any help would be so appreciated! Thanks!