I have a problem with the site
When paying via PayPal it appears 

broken content-length header

Use the PayPal Demo Portal SandBox 

As shown

no idea what you're asking you need to provide more details of the error,

 [proxy_fcgi:error] [pid 18760:tid 139772756436736] (70007)The timeout specified has expired: [client 1.1.1.7:55668] AH01075: Error dispatching request to : (polling), referer: https://www.sandbox.paypal.com/
 

under webserver domain config and webserver main config you've options to set  apache timeout templates choose that template for your website and check,