Resizing the /data partition (rooted) My app market (Google Play) has a problem. I can't install any apps on my phone (Lenovo, rooted) because of "There isn't enough space in the disk", but actually there is. After asking a friend, I moved apps to the SD card. After more tries, I understand that the apps are installed on the /data partition and when it is full, I can't install more apps.

When typing df I get: 

# df
Filesystem               Size     Used     Free   Blksize
/dev                   482.1M   128.0K   481.9M   4096
/sys/fs/cgroup         482.1M    12.0K   482.0M   4096
/mnt/secure            482.1M     0.0K   482.1M   4096
/mnt/asec              482.1M     0.0K   482.1M   4096
/mnt/obb               482.1M     0.0K   482.1M   4096
/system                885.8M   679.5M   206.4M   4096
/data                  908.5M   825.9M    82.6M   4096
/cache                 123.0M     4.0M   119.0M   4096
/protect_f               8.8M     4.1M     4.8M   4096
/protect_s               8.8M     4.0M     4.8M   4096
/mnt/cd-rom              1.2M     1.2M     0.0K   2048


I know from another app that there is more free, not mounted space. 

How can I resize this partition? If more output is needed so tell me what to type. Thanks.
As GiantTree correctly pointed out, That not mounted space might be something the device uses in something like an emergency mode to restore the device. More precisely: it not only might be, but it is. Your df output e.g. doesn't say anything about the /recovery or /boot partitions. And there are even more we are not aware of.

Another argument against re-sizing: You won't be able to install any Android updates anymore, as those often come as "images" to flash (replacing entire file systems) – which then no longer would match the partition size, causing the update to fail to flash at best, or bricking your device at worst.

If app2sd no longer gives you enough freedom, you can take a look at link2sd – which is able to not only move the entire app to your device's external SD card (App2SD only moves parts), but can even move more, such as their data files and libraries.

For some more background, take a look at the link2sd tag-wiki, and also the app2sd tag-wiki.