This is a user to user forum and not a "MAGIX Sales team". If the offer to "upgrade to VEGAS Post" that you have received is not clear to you even after clicking "Upgrade now", please try emailing sales@magix.net and explain your problem.
You might also want to peruse the product website to find out the purchase options
(Click the globe button on the black bar at the top of that site to select your area's version of that URL which may be in a language more familiar to you).