Error 500 before installing. PHP version.

Hi!

I cannot access the installation process, as I get an error 500 when going to the akaunting directory on my website. The root domain works well.

I checked the PHP version on my server (Plesk latest version) and my version is 5.3.3 by OS vendor. I cannot upgrade the version, it seems to be the latest available in my panel... 

Could you tell me how to proceed? Thank you!

Solved by installing the new PHP versions in my server. Thank you!