sharing on facebook problem

i recently created a blog texnologos.allalla.com and i used the theme GamesMania but when i try to share a page or a post on facebook, it looks like this i saw that a lot of people had the same problem but even if i tried all the possible solutions, the problem still exists. I also thought that when i was changing the code of the theme, i may deleted something but i transfered the theme again via ftp and there was the same problem, but i don’t think it’s theme’s problem because in the demo when i share everything is ok. please help me