About the responsiveness of my website

hi, i checked my website in other mobile. it is not responsive. in the attached image they have two columns in mobile so some text overlaps. i want to make it only 1 column in mobile phones so it will be presentable. i have learn basics in bootstrap so can you give me some guides on where can i edit this thing? what file?

not responsive. https://i57.tinypic.com/2ijopoz.jpg
i want to be like this. https://i60.tinypic.com/6xvh9w.jpg

https://www.ads-software.com/plugins/real-estate-listing-realtyna-wpl/