Travelify mobile responsiveness not working properly

I’m using the Travelify theme for my website and it works great ! But the mobile responsive isn’t working correctly !! I would like my website to be responsive same as this website how can i do that??? And this is my website

You have broken down theme functionality with your custom implementations. Remove all custom CSS and start over because it is easier to start fresh than trying to find what you did wrong with the code.

Custom implementations done via Theme Options or WordPress customizer are not one to be blamed and you can leave them as-is.

i didnt modify anything, the only modifications i made were on the upper section of the CSS file i didnt touch the mobile responsive. i will try to fix the problem thank you very much Mr.Aigars, the theme is fantastic.