I like how, for a change, the website fits the entire browser width. Good use of space there.
- The colour scheme can give an appearance to the website as 'busy' and 'disorganised'.
- Your global navigation menu has a default cursor style, rather than a pointer cursor.
- The general layout on the Home page is quite busy too, margins and gutters aren't consistent. You could improve this by lining up elements.
- That advert to "DOWNLOAD" diminishes your website credibility, it's the type of advert users are used to as "scams", because it is disguised as a genuine website feature.
- You have multiple heading
<h1> on your Home page, which compromises SEO. You should only have one per page.
- You have 15 W3C validator errors on your Home page http://validator.w3.org/check?uri=http%3A%2F%2Fgreckapilka.cba.pl%2F&charset=%28detect+automatically%29&doctype=Inline&group=0
You should fix these errors and on other pages, as it's likely to improve cross-browser compatibility.