Website and Database Maintenance DotNet Environment

We have a back end website that manages an event platform. The event platform is [[login to view URL]][1] Due to changes and new features of this event series, we need a programmer who can do AD HOC changes to the back end dot net website to upgrade the functionality. Examples of what is needed: Adding a drop down box for countries for the user to select in their profile rather than adding a country manually. Changing the pages to show data from a sql server database. Changing database tables to add new fields, then allowing the display of those fields on the web pages. Applying filters to the data so that different data sets can be returned to the web pages. Finding and fixing errors in the code where functionality is not clear or broken.