It sounds like your grievances are around Firefox being too slow. While I'm unable to help with that, if your websites are loading as a desktop layout, then click the 'three vertical dots' menu icon and uncheck the 'Request Desktop Site' option. If the option is already unchecked, then the site may not have a mobile-friendly version yet.

Hey man I used chrome opera uc and finally Firefox I find lot of difficulties in smooth browsing lot of failed downloads hanging lot of times I have 2gb ram I think its enough no taps and its hangs i have a high speed net connection still the video buffer it was not occur in other browsers and website loading was very slow even it hangs when I typing this review

No I am enabled mobile user agent not desktop site I don't even need