Is it possible to do something with chocolate so that it does not get hard anymore so that its consistency gets something like the caramel in a mars/snickers bar? What precisley would I have to do to achieve that?
Perhaps a thick ganache might meet your demands. It wouldn't be as sticky as caramel though. But take a look at this question. It mentions adding some honey and butter to the standard ingredients, cream and chocolate.
If you have questions on how to make ganache, watch this video or one of the many others available on the internet. Simply said, heat up heavy cream and pour it over chopped bittersweet chocolate. Stir till all the chocolate is melted and you have a nice, smooth consistency. For your purpose, use at maximum the same amount of cream as chocolate. Add some more chocolate if it's too runny. But know that the ganache will become harder/thicker when cooled.
I can think of a few ways of achieving this:
The easiest (although not strictly using pure chocolate) way is by combining some sort of syrup like honey, agave, golden or corn with cocoa powder. This would give the sticky texture your looking for, not go hard once cool and taste of chocolate. Here a recipe link, it's from a vegan blog, http://karensvegankitchen.blogspot.com/2010/09/thick-gooey-chocolate-sauce.html.
Another option is glacage chocolate which is a kind of fancy French chocolate glaze. It's probably not quite what your looking for but I'll explain anyway. It's made in its most basic form by combining chocolate with gelatine. This gives it a gloupy texture, although it is used in patisserie for it's mirror like shine. Here a recipe link if you do want to have a look: http://patissierjourney.blogspot.com/2010/08/glacage-chocolate.html.
Another final idea is making a typical ganache (chocolate and cream in a ratio of 1:1) and adding some corn syrup or other sugar based syrup. Which could give a sticky caramel texture and choclate flavour.