Website slow on Android devices and other website response time issues..

Hello,

I have shared two screenshots.

1. Pingdom monitoring report: This report for last 1 month shows that the response time of the website was more (about 12seconds) in mobile devices. Which is very high. I myself browse my site and find that the pages get stuck suddenly and dont load while other sites load pretty well. This mostly happens with 3G connections while it works abosultely well on Wi-Fi. I have also installed some tracert apps on my android mobile and found the tracert perfectly tracing to the server IP. So, what could be the cause of sluggishness on mobile devices and esp for my site?

2. The report also shows that the front-end load time is high. What does this mean? Does it mean that the front end stuff like images are taking longer to load?

3. Pingdom 1 month website response time report: This screenshot shows that the average website response time is around 600ms. As far as I know the website response time should be low around 300-500ms. The DNS response time is around 50-60ms but if the website response time is 600ms, then perhaps the issue should be with the server. Any idea on what parameters I should look into and what could be a possible solution?

Any help from server optimization experts will help.

Regards,

Ravi