You can use PHP and MySQL on the web server (server where your website lives). Send a request to PHP on your website like mywebsite.com is available for purchase - Sedo.com and PHP going to get the value from MySQL and return it to GDevelop. BUt you need to write the actual PHP code to get the value from the database and you also need to setup the database yourself…
LIzard-13 just linked a tutorial for you in your previous topic:
You may want to take some free PHP and MySQL courses first if you don’t understand it. You can find plenty on Youtube.
youtube.com/results?search_ … P+tutorial
youtube.com/results?search_ … L+tutorial