Problem when loading pages

Hello,

using 3.4.2
theme Esplanade by onedesigns
child theme with few personalisations

here is the url of my site (site is not yet complete, so please be kind to me 🙂 )
http://www.atelieranastasi.com

as you can see, if you click in the menu the complete page is re-loaded which give the impression of a flash … very uncomfortable.
How to solve that so that the pages are load nicely (like here for exemple)

thanks for your help.