my WP tooo slow in loading, and crashes immediately

Hello Guys,

plz i need ur help, i just installed WP, and used 1 ready made WP theme, it is tooo slow in loading, and when it is loaded, after 5 or 6 clicks on Menus browsing the website, it crashes. plz check it by urself :

https://www.mega-choix.com

iam using WP Super Cache but no results.

When i restart my router, it works just fine, but after 5 or 6 clicks again, it crashes.

can u tell me what is going on ? and can u advice me what to do exactly plz ?

Thank you very much ??