Hi Benjamin,
There are around 20 Notes for solving the issues of IE11 in CRM webui
How ever for the Quick Solution you should enable the enterprise mode in your system.
Enterprise mode is nothing but asking the system to behave as it was behaving before.
Check out the link( In the point 2)
https://msdn.microsoft.com/en-us/library/dn640687.aspx
In the point 2 you have a download which you can download and add your site for example xxxx.com
then it should work fine.
thanks,
Rajesh P