Hi Lidwien,
With the partition update the phone now works with MTP (media transfer protocol).
This protocol is not standard supported by Linux, but there is a way to resolve this.
As just discussed on the phone I would like to direct you to the following website for more information on how to resolve this: http://www.xda-developers.com/android/use-android-mtp-on-linux/
Here they explain how you co make your internal storage to be recognized again.