It's working thank you all!
For those with same problem:
Open console and type:
sudo chown -R $USER:www-data /var/www/your directory name eg. masterplay.cz
Then:
sudo find /var/www/your directory name eg. masterplay.cz -type d -exec chmod 775 {}\;
And the last one:
sudo find /var/www/your directory name eg. masterplay.cz -type f -exec chmod 664 {}\;
Dont forget to replace "your directory name eg. masterplay.cz" with your web server directory!