Website having blank grey area when Opened in Smartphone

Hi,

I am using Magnet theme by 99theme. The problem I am facing is that when Homepage is opened in Smartphone it has lot of blank grey area or so to say it is not responsive. However, when opening post pages everything is perfect.
Website : https://www.techuntold.com
Issue is only for smartphones and everything works fine on computer.

I have tried uninstalling all the plugins but nothing is working out.

Any sort of help is highly appreciated. Thanks a lot