Hi
Thanks for contacting us. SP Page Builder (Pro) can be updated or upgraded like any other Joomla! extension just by installing a new version on the current one. You do not have to uninstall the previous version; in fact, you MUST NOT do that. Make sure that your hosting account is using at least PHP 7.0.x, you can update SP Page Builder (Pro) by installing a new version on the current one, without uninstalling the previous version.
What happens with the content I allready have?
It will not change. It will be the same as before.
NOTE: Make sure you have a full site backup before making any changes.
-Regards.