Subpage Question?

well that's a subdomain and most domain hosts allow those. Check with your domain provider to see if a subdomain option is available. This will add a directory to your hosting if you host the site with them or you can configure it's DNS settings to your host to run a new site on it. If this is too complicated then you are left with the option of polishgoals.com/blog or something to that effect.

that doesnt really answer my question though :/ can a second php-fusion run on this subdomain

Yes it should be able to do that

now can someone please tell me how :) because i have no idea how to install it on lets say blog.polishgoals.com u know?

thats a question for your webhost

there should be an option in your control panel to create subdomains to specific folders. set one up and install your script in that folder. note that it might take some hours until the subdomain is available.

Login to your Server [Host] im sure youll see "Sub-Domains" somewhere,

I THINK youll have to change the table prefix from _fusion to something else in order to install a second script on the server without them interferring ??

And you can use the same database but make certain you choose a different table suffix when running setup for the second site.

ok thanks guys. one more question... do i have to change anything in the code or should everything work?

Not really.
Like already stated - use a different prefix for your tables at setup (default is fusion_ - you can't use that on both sites, or your first database will get overwritten by the second one)

Secondly, i would recommend editing /includes/multi_site_include.php on the second site.

Find:
// Cookie prefix
define("COOKIE_PREFIX", "fusion_";

Change the cookie prefix on the second site to something different, like:
define("COOKIE_PREFIX", "sitetwo_";

to avoid login problems cased by conflicting cookies.

what if i set it up on a second database? then i could avoid the above mentioned changes?

Yes. That's the simplest solution. Just set it up the same on a different database.