I got one of these cheap readers. I noticed the list of the latest firmware for the trekstore firmware updater is fetched from http://id.readerportal.de/api/TrekStorProduct?os=win

According to the firmware update list, its name its "eBook Reader 4 Ink - ND".
The latest available firmware version is EBR40-WB-2.0.53.img.zip

Anyway, I was wondering if someone has found a way to make the device put the ebooks in some kind of hierarchy (folders). Creating folders on the USB storage doesn't do anything (you can still read them if they are in a folder however). The list of books in the GUI gets unwieldy quickly.
Do you have back-up of this firmware? becouse this site is offline
Given that the OPs last post was in 2014, I suggest you PM instead of waiting for an answer here may never happen.
Thank you for help
No I don't have the file any longer and I no longer have this device. Sorry.

The URL

http://web.archive.org/web/20170129112538/http://id.readerportal.de/api/TrekStorProduct?os=win

still works, it points to

http://ota.readerportal.de/ebookreader/EBR40-WB-2.0.53.img.zip

however that file is not archived by archive.org.
I have mirrored this file.
https://ipfs.io/ipfs/Qma9f415McoxQC6jbyY2rTLsgggSP5yy2LwGncUiQEPDpP