Basic theme building is quite easy with minimal knowledge of PHP. There are good guides to start with, e.g. these:
http://www.concrete5.org/documentation/how-tos/designers/making-a-t...
http://www.concrete5.org/documentation/how-tos/designers/make-a-the...

I'd suggest also taking a look on this add-on because you have two languages:
http://www.concrete5.org/marketplace/addons/internationalization/...

The part where it might be hard, is customizing the blocks to your need. However, there are good guides on that as well, so I'd say go with it. From the design of the site I can clearly see that you are already familiar with this stuff, so if you know just a little bit of PHP, there shouldn't be a problem.

And even better news: once you do this, next time it's 100 times easier!

Thanks for pointing me in the right direction.

Just a few questions.

1. My design includes some jquery stuff, specifically a scrollbar to
scroll the content (insteadf of the ugly default scrollbar in the
browsers). Will this be a problem? I want the content to scroll
without the rest of the pahe following it.

2. Each page in my current design has a different image in a separate
div on the right side (exept the image gallery). How do I do this in
concrete5? Can I define each page (with a separate image on the right
side) as a separate page layout (as full width, two columns etc are in
concrete5). And if yes, can I name them whatever I want? If yes, the
user can define for instance the blog layout if she is adding blog
content or the bio layout for editing the bio text.

Hope you understand what I mean, a little hard to explain.

HI,
Nice site, nice concept.

Yes, you can do all you want do with C5.

Javascript: You do not need jQuery (built in to C5), you do not need typeface.js (use fontsquirrel & CSS)

Rounded corners - CSS.

Scroll - Overthrow.

Add a page then place any image in sidebar.

Bottom line is YES with C5.

What you could do is optimise the images.

Hope that helps

Answers to your questions:

1. Yes, you can do that all with concrete5. jQuery is already included in the core (as stated by 55webdesign), so you don't need to load it again in your theme.

2. I would do it with just as a right column area, I really think your site needs two templates:
- front.php (where you select the language)
- default.php (for all other pages)

And just design the default.php so that it has two areas in the left column, one for the scrollbar content and one without scrollbar (e.g. for press page where you have content below scroll).

In the attached image I demonstrated how I would split that page into concrete5 areas. This way each page can have their own content in each area, except the Global Areas which are the same for each page (these area marked as Global in the picture).

For the blog, I would build that with composer:
http://www.concrete5.org/documentation/how-tos/editors/setting-up-a...
http://www.concrete5.org/documentation/how-tos/developers/create-a-...

And because you have used e.g. "blockquote" elements in your source, that might be hard to keep consistent with the built-in content block. To keeping them how they should be, I would suggest taking a look at the Designer Content add-on:
http://www.concrete5.org/marketplace/addons/designer-content/...

Fantastic response. Makes me convinced this is the CMS to try out. I have made websites with Joomla, WordPress and CMS Made easy, but this seems to be the best solution for me (I need to have control over the design without spending months learning how to do it).

I am not that "fluent" in php and CSS, just look at what others have done and try it out. The only thing I am not sure of now, is what you mean about JQuery being embedded in the C5 core. Is it the JQuery core application that is built in, or is it all the scripts I use? For instance, my scrollbar is now called with a DIV that uses this script.
Can I use my scroll bar, or do I have to find an add-on that does the job?

Update, is this what you mean?:http://www.concrete5.org/marketplace/addons/scrollbar/...

The core jQuery script is already shipped with concrete5, so you don't need to have the manual jQuery inclusion in your <head> that you currently have.

You can use your exiting scripts, but they are not bundled with concrete5. Include them in your theme's folder and add references to them correctly as the tutorial video posted above shows (by Andrew, in the first post).

For your update: you can buy that if you want it straight out-of-the-box but it's not necessary if you just include the script in your theme's header you currently already have and reference the scrollable areas correctly.