Repsonsive Advise Generator using NODE.JS / EXPRESS.JS / EJS

Hi guys! This is my first website using node.js, express.js and EJS! I ask everyone for some advice on how to improve my code, especially about the "app.post" section. In this case my code redirect to the main page, but i would like that, when presse the button, it retake API values without reloading the page. Thanks a lot for your time! Have a nice day!