Just checked your site, and you need your developer to look in to the following thigs.
1) Make sure EVERY item is loaded via HTTPS, currently you got some items that loads via HTTP this makes the browser show your site as insecure.
2) You need to look in to the speed of the site, the site is very slow currently, and for me sitting in Denmark the load time is 5-8 sec, this will actually loose your customers to, according to GTMetrix with there London location used is 13 Sec loading time this should be a main focus to fix - You should read https://blog.kissmetrics.com/loading-time/
3) Leverage browser caching - needs to be sortet out to, right now you dont use the browser caching at all, and this is important since revisitors have to load the elements over and over again when they switch pages on your site, with Leverage browser caching turned on, they only have to load it once (unless they flush there browser cache) and this will give some improvements in load, not for first visitors tho.