Hi,
---Slider Question
I don't think that slider will display videos. Your best bet is to go pickup a custom slider that has the specific functionality that you are looking for. There are probably a few dozen sliders , both free and premium, available from codecanyon or the free wordpress plugin repository. A good choice to start off with would be http://wordpress.org/extend/plugins/slidedeck2/ , which is free but has premium options as well. And there are a thousand ways to customize it, and there is no need to write any code.
---Title Font Question
I am not sure what font you are using without seeing your website. They are probably cufon enhanced. What fonts do you normally use to display Slovenian letters?
--- Logo Question
You can change the logo by first uploading the logo you want using media or ftp to your server and then editing the style1.css file in the css folder ...(if you changed the 'CleanCut - Skin' option in the General Options of the theme (there are total of 5 skins) you would edit style3.css or style5,css) changing the number based on which skin you've chosen in the options. If you haven't changed this setting then style1.css is the default.
find line 39 which should look like
background: transparent url('../images/skin1/logo.png') no-repeat top left;
and replace it with the url of the image you've uploaded of the new logo. You can of-course use ftp to go to the images/skin1 folder of the theme , call your new logo by logo.png and upload and overwrite the demo logo.
------Smaller Column size.
To change the size of the 4 columns , please open up style.css located inside the theme directory and find line 111 which looks like
.fullwidth .one_fourth, .fullwidth .box_small{width:210px;}
and change 210px (the current width of each box) to something smaller, you can try 190px and see how that looks, and tweak it from there.
------Translation
Please make these changes, and when finished, rescan the theme for strings.
In file kclass_display_box.php in the /framework/classes/ folder, please change line 123 to look like
echo "<a href='".get_permalink()."' class='more-link'>".__('Read more','cleancut')."</a>";
Don't forget to rescan for strings.
Thanks,
Nick