Everytime I open up the editor this thing pops up: These options are greyed out so I can't do anything but press cancel everytime. I thought that I installed these once, but I'm not sure.
If so check the Do not showagain option and select Later. This will stop the Download extra content dialog appearing after start up.
If you did get the dialog previously and selected the Do not showagain option and OK then reactivate the popup dialogs in the Program Settings as shown below and proceed as above
That message is asking you to accept either, the installation of an update, or the "installation" of your registration key. It always appears after an update and after you have chosen to "re-register" your software. If you click "Yes" you should then receive a message confirming that the update and registration has been acknowledged by the Magix server and advising you to keep a careful record of your registration key.
If you are also receiving the message that the OP is seeing, the fact that you are not accepting the "Installationsmanager" message could well be the reason, since you are not confirming acceptance of the completed installation and registration.