Desktop compared to Mobile version of the site looks off

I know this might be a newb question to many of you but I'm pretty new at this and seem to have hit a roadblock. The issue that I'm having is that on the desktop, my website looks perfectly fine, everything in line but when I view it on my mobile, the words on the menu bar overlap if they are more than one word. Also the pictures look out of place. If you can help me with this issue, I would highly appreciate it. Thank you for taking the time to read this and for your help.