You can optimize your conversion rate with only few technical adjustments. The loading speed of your web shop is one of the most important aspects, as users are usually very impatient. There are enough alternatives to your online shop out there… If the loading times are too long, your customer will quickly decide to visit a competitor shop.
Time is running …
On average, a charging time of three seconds is considered appropriate. Pages that load longer are closed. This impatience affects not only the loading time of the online shop, but also the time required by a search process or the loading of product detail images. Studies assume that an additional second of loading time can reduce the conversion rate by up to 7 percent. 
Especially web shops offering hundreds of thousands of products and variants are dependent on an optimal loading time of their overview pages. Ten years ago, Amazon recognized the connection between loading time and sales in a study. A 100 millisecond increase in loading time reduced Amazon sales by one percent. 
Vodafone has already had to find out how decisive the loading time is for success. Their web shop once called up a loading time of 35 seconds when the accessories page was first opened. Normally, KPIs for such pages are a maximum of 3.5 seconds.
Kissmetrics’ monitoring and performance tests also showed that nearly 80 percent of customers who were dissatisfied with website performance would not buy from the online shop again.  Web shops should therefore work with caching strategies on the application server instances or in-memory cash tools to improve performance.
Another point that makes your online shop popular with your customers: the perfect responsive design. As a shop owner you have to make sure that your offer is also optimized for mobile devices, because shopping via smartphone or tablet is constantly increasing. This results in special requirements for the operator. For example, the layout of the web shop must be responsive or a separate website must be created for mobile devices. This is the only way to ensure that the customer can also shop optimally from mobile devices.
,  https://www.findologic.com/zusammenhang-von-conversion-rate-und-ladezeit/ (17.08.2017)
 https://blog.kissmetrics.com/loading-time (17.08.2017)