How can i elimiate areas of my form that are not needed based on selection criteria?

I have created this form and want only the information that is filled in sent in on submission.

Example if the user selects "Change existing vendor information" i only want the information that pertains to that page to be submitted when the user clicks the submit button. All other required fields should be ignored.

I also want only on that page "change existing vendor information" when they select the item from the drop down box i want only that area displayed. As of now it looks like the no matter what is selected all of the "to be changed" areas are showing. ( hope that makes sense). If they select phone number, i only want that area to show. If they select physical address and phone number then only those two areas should show.

I have inspected your form and I saw that you are using skip to page conditional logic base on selection of the field "I would like to".  As far as I can see this part is working correctly. I made  test on my cloned form and only data from page that I was redirected to was included inside of email Notification. 

For the second part, you should use conditional logic to hide/show fields base on user's answer. Inside of this guide you can find how to do it:

How to Show or Hide Fields Base on User's Answer

Let us know if you need further assistance.