How optimize my forum to make it faster?
 

This tool shows a lot of things that should be done in order to make a vB forum faster: CSS sprites, minification etc.

http://developers.google.com/speed/pagespeed/insights

Is there a modification (or a manual) that would help with fixing all of it?
Thanks.

well, this topic is very long and has been discussed many times... it is an endless topics anyways...

but to some point, you can refer to this article... and of course that depends on what vb version you use...and whether you have custom or default style as well...

FractalizeR: VBulletin 4 extensive optimization guide (Part I)

FractalizeR: VBulletin 4 extensive optimization guide (Part II)

Step by Step guide to speed up your VB4 OR VB3

if that's too difficult for you, then you should send me a PM with your vb version and style type as well as a test result from GTmetrix

Cheers