my internal storage is at 84% (not the sd cards!).
where is it in the file system & what & how should i
delete stuff. is there any cron job to automize this?

thx again!

Did you try unstall?

Hi,
yes, one of the posibilities is to uninstall some applications that you do not use.
Other option is to move all your documents from "Documents" folders (under your device name in file manager) to some one of your memory cards (or internal storage for N810).
When device is reflashed there have almost 25 MB that can be freed inside these folders. 10 MB is a Video file for Tablet, almost 5 MB in songs and almost 10 MB as PDF files (manuals for all languages).
Third possibility is to search in to this forum and read how to clone OS to your SD card and this will give you a lot more free space for applications.

Yeah if you want more space probably the most effective solution is to clone your internal card to SD, then you'll have 2GB instead of 256MB, much nicer.