Hey RBGE
Thank you for your reply!!
"I'm not sure why it's saying you need to upgrade given 1.14.1 is currently the most recent version "
I don´t know what the problem is with the Version. The message is not showed the hole time. Sometimes it´s all alright.
"I'd advise enabling the fileinfo extension if you're going to be uploading files - after uncommenting the relevant extension line in php.ini, remember that you need to restart IIS for the changes to load."
I already did this a several times, but it doesn´t work. It Looks like, that the php.ini don´t "synchronize" with the IIS. My problem is, that i can´t install the PHPManager, because of our group policy.
Update:
I found my problem in sight of the extensions. I don´t know why, but the IIS is taking the php.ini-File from C:\Program Files\PHP\v7.0 and not from C:\Program Files (x86)\PHP.
I was editing the hole time the files in the x86 directory.
But sadly it doesn´t solve my problem with the attechments. There is already the error "File Upload Error - undefinde 500".