I will submit your website directly to google and send you their detailed report for you to give your webmaster.
This report will give you numbers of how you score out of 100 for the following - mobile-friendly, mobile speed and desktop speed.
These stats are from Google.
1) People are five times more likely to leave a mobile site that isn’t mobile-friendly.2) Nearly half of all visitors will leave a mobile site if the pages don’t load within 3 seconds.
3) 9 out of 10 people say they use multiple screens for such tasks as booking a flight online or managing their personal finances.
Test how mobile-friendly your site is.
Find out how well your site works across mobile and desktop devices.
Just good info for five bucks from kiwifiver.
Detailed Website report