Have got this website that is working on wordpress.
website speed for desktop version is around 75-80 but for mobile is lesser than 50.
Have tried different plugins but seems not working.
Images are the most common reasons that websites perform slow on mobiles, so you must check if they are optimized for smartphones. Avoid unnecessary and complex designs and visuals to lighten the burden on website. Also, sometimes page designs are not compatible with mobiles, so check the framework for mobile.