The problem is that the file manager does not show you the ascx files.
This is for security reasons as allowing an admin to change the ascx would allow him to get to the host password, DB password etc. and thus get access to all data also from other portals.

(DNN can be used with multiple admins for different organisations in the same installation)

You can do this to get access, but don't forget to undo it..

When you have a host account, you can do this:

Host > Host Settings > Advanced settings > Other Settings.

Now under "Allowable File Extensions:" add ,ascx at the end.

Sync the file manager, download the file, edit it and upload it again.

When done, go to

Host > Host Settings > Advanced settings > Other Settings.

And remove the ,ascx from the list

I seem to be absolutely stupid. Well, I don't see the "Host"-Folder, so I suppose, that we're not host, only admin (wich is surprising as this is the only account for our c buompany..). Maybe this is because another company made this site for us... so maybe they're host.

And how can I see the .ascx files in my DNN folder with FTP (don't even know what that is) or Remotedesktop? And is the DNN Folder simply the folder in the Filesystem when logged in?

Sorry for my stupid questions but at the moment, I feel lost :P

Greets Helpseeker

I think you better contact the company that build this website and/or the one that created the skin for you.
I guess they didn't give you a host account or FTP access, without that you cannot access the skins ascx files.

Host account is the SuperUser account in DNN.
FTP = direct upload/download access to the websites files, unrelated to DNN