unable to update theme – Help please!

Hi! I been trying to update the theme several time and it´s impossible. I downloaded the envato market plug-in and is useless, always the same error “Installation package not available” I tried to update without this tool and the error is: “The package could not be installed. The theme is missing the style.css stylesheet. Theme installation failed.” or “file already exists. Theme installation failed.”

And what about visual composer? Can´t update it neither, need the license number that i don´t have, of course.

So, what should i do? I´ve tried everything, read all possible solutions in internet, this forum and nothing works… Should i buy a new theme from other autor? Sorry, i am very upset about this problem.

Somebody had the same problems? Can anybody help me, please? Thanks!