Vantage theme doesnt work properly (Mozilla didnt show text, premium doesnt work)

Hi,

i have site with wordpress 4.2.2 (http://www.sevatech.cz) and vantage theme 1.4.2 and page builder 2.1.2.

#1 I want buy premium vantage, but it shows me blank page (http://www.sevatech.cz/wp-content/uploads/2015/05/Snímek-obrazovky-2015-05-31-v-13.37.19.png). I reinstall theme several times, didnt help at all. How can i resolve it?
#2 My friend with Windows + Firefox shows me that my page in this browser didnt show any text on the site and also nothing from page builder. It really bothers me. Thanks for help!
Screenshots:
http://www.sevatech.cz/wp-content/uploads/2015/05/11294461_10204337005411786_379749586_o.jpg
http://www.sevatech.cz/wp-content/uploads/2015/05/11227453_10204337022212206_527561879_o.jpg

URL: http://www.sevatech.cz