Menu is linked with com_content, not com_flexicontent

Hi Rehne,
I've already import the Joomla structure into FC. FC is filled with the items(articles) which I already had before.
I'll give you an example:[attachment=2:b0vvcgv9]<!-- ia2 -->screenshot1.jpg<!-- ia2 -->[/attachment:b0vvcgv9]
In screenshot1 the article 'Actorrol A10'(article ID=114) is an old article that I had before installing FC.
After installing FC a FLEXIcontent section appeared in the drop down list.
[attachment=1:b0vvcgv9]<!-- ia1 -->screenshot2.jpg<!-- ia1 -->[/attachment:b0vvcgv9]
In screenshot2 the article 'Actorrol A10' is the same article as the one above, but with another article ID(529). Here we are still in the Article Manager.
[attachment=0:b0vvcgv9]<!-- ia0 -->screenshot3.jpg<!-- ia0 -->[/attachment:b0vvcgv9]
In screenshot3 you can see FC. The article above is a duplicate of the one with ID 529.
When I edit this item in FC, it will change the one in screenshot2, but not the one with ID nr 114.

Is this right?
I wonder if it's okay that the FC section appeared in the Article Manager.

Is this right?

as I see it YES
if you use FC
you Do not need the Joomla Article Manger (why!?)

It seems so that your problem is
that you have duplicate items

why I can not say
but try the following
delete a double item but not from the FLEXIcontent Section but the others from the joomla section (take one you do not need)
After this look if the second intem is still present (it should be)

If so,
you can delete any duplicate items
but not from the FC FLEXIcontent Section
and after that only use FC to edit/create items not the Joomla Article Manger

I wonder if it's okay that the FC section appeared in the Article Manager.

Thats ok!

Usage of Joomla content and category tables for content backwards and forwards compatibility (this means it extends the com_content instead of replacing it)