Grey folder in iCloud Drive
So I fixed it by using the terminal. I moved all the content of the grayed out folder and to a new one.

//edit: a more detailed description on how I solved this problem:


with the help of the terminal I moved all the files in the strange behaving folder to a new location. Using the mv command. E.g. cp ~/Library/Mobile\ Documents/com~apple~CloudDocs/YOUR_BROKEN_FOLDER/* ~/Documents (the * is for all the files).
Once this folder it empty you can safely remove it with the rm -f command. E.g. rm -rf ~/Library/Mobile\ Documents/com~apple~CloudDocs/YOUR_BROKEN_FOLDER
If you want you can now recreate the folder normal in the finder and it should appear normal again.