Are the cable housings inserted into the brake handles all the way? (and any other housing stops)
Is there a "thumbscrew" adjuster on the brake handles (or elsewhere) to give you a bit more slack.
Is there another bike like yours that you can look at?
Maybe you can search the web and find a link to a brake system that looks like yours and then post it here so we know exactly what you have.
"sort of U shaped" and "technical lego" really don't help us a lot. Go to Sheldon's site and learn the terminology (it'll only take a couple minutes). There's multiple types of brake systems. Knowing exactly what type you have helps us to help you.