Installation-webserver-error 500-400

Hi there,
i'm trying to install grav but i keep getting Internal Server Error 500 and 'additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request'

apache server, PHP 5
any advice would be much appreciated!

https://learn.getgrav.org/troubleshooting

Also, which version of PHP 5 are you using? Grav supports PHP >= 5.5.9

thank you!
PHP Version 5.3.29
i had a go to the troubleshooting advice on that link but without luck....

You need to update, or ask the hosting to update, the PHP version.

thanks! i'll try that...

great! we got now we have the PHP Version 5.6.20 and the installation seems to work!