You can use the Media Queryies from CSS in the Sass files under ‘styling’
If u are using Visual studio code for styling then go to the theme folder of your memdix application where u can find web and native folder, or else in mendix u can find under styling. There you will find main.scss and custom-variable.scss file. Then create a new custom scss file and using media query make your application responsiveness. Then import that file in main.scss file and run the code.
I hope this will help you.