Sorry, it is actually "Other installations" 1.9 gb within Application data. Thats what taking space. I have nitdroid installed before which I deinstalled a few months ago. Anything to do with that maybe?

Emails?

Check the size of /home/user/.qmf via terminal and nitdroid should be in /home/nitdroid ; if you are not using it remove it too

Wow!! I deleted the .qmf folder and now other applications are only 920.1 MB.ry much!! It seems that this solved some of the problem, I think I will do it regularly.
Thank you!
However when I try to delete /home/nitdroid, I get a Privilege denied warning message.
What else can take space?
Cheers so far, I'm really grateful!!

No probs, that folder is where your emails are stored so I don't think you want to delete it regularly instead set your emails to download headers only instead of "full messages & attachments". This way only important messages which you want to read etc have full content downloaded.

Are you root (devel-su) to delete /home/nitdroid?

OK. I open My Explorer and go to System volume (/), than go to home , mark nitdroid, i do a longpress and select delete. Here I got the message that Unable to delete '/home/nitdroid/': Privilege denied. What is the command to delete from terminal? I go devel-su, and rootme. What is after?

(-f=force -r=recursive, try rm --help for more info)

Well, I tried ands it says cant' remove file, directory not empty.
But I managed to delete an empty folder with this command. Where can i find more commands like this?
Ladoga, you helped me a lot, cheers Mate!

use it as root, i mean..

first get root access by following these command:
devel-su
password is 'rootme' until u have changed it.

then the command mentioned above and you are done.

Yes, this is what I do exactly, but still privilege denied...

Do the following:

If it still doesn't remove it then use opensh/ariadnesh