I want to create a sort like of abc in my website. I understood that this is also posible by K2
but then how?

can anyone help me with this?
see also example how i want to integrate this in my website

Hello Marcel,

It can be done with K2. It requires coding though. You can look for an extension at the JED or at getk2.org/extend of you have to create it your self. (Either creating a new K2 Category template or preferably a new component for items,)

If it is categories you want to display then you can simply mod_menus (The letters being a menu item as well ) and a simple JS script so you can scroll down to the letter you want.