Slow loading time for a eshop built by an open source software

I am working on a eshop and the time is very long to loading

So I have check the tool to analyze

http://ift.tt/1O3iDZH

and

http://ift.tt/1XxTn8h

The problem is that the site seems wait a few second before actually download the resource. Are there any way to track is there any JS coding / PHP coding takes the most of time ? Or any approach to debug that

Thanks a lot for helping.