The screenshot you have attached is the GTMetrix page speed of that particular page. If your page loading speed is low then following steps to improve the page speed:
- Minify the JS and CSS.
- Merge the CSS and JS.
- Inform your designer to optimize the images using lossless compression.
- Proper scaling of images needs to be done.
- Use Content Delivery Network for static resources.
- Enable gZip comperssion and add expire headers.
- If the page has many third party request then reduce those request.
These are the ways to improve the page speed.
Also you can verify the page speed using the Google Page insights(https://developers.google.com/speed/pagespeed/insights/) and also there is an google chrome extension "Page load time" to verify the page speed.
Try JMeter a performance testing tool to measure the performance of the web applications