Hello,
1) We have installed the cache plugin to speed up your site. And speed results are not bad https://tools.pingdom.com/#5b58bcbf21800000
2) Optimize your images to reduce the page size. You may use https://tinypng.com/ and save up t0 80% for example result for one of your images http://prntscr.com/pa966d
3) Site speed depends not just on theme or plugin but on the server. I would recommend you to check this item especially if sometimes site works ok and very slow the other time.
If you need professional help with the site optimization submit the request to WPKraken team because our support does not cover the individual site optimization. We can help you only with theme settings or bugs related to theme settings.
Regards