How to extract .image from recoever-image.exe / Wie die .image von recover-image.exe

Find any other firmware image (for the same model, version does not really matter) with the "image" extension (these files are simply tarballs without the proper extension) and extract the contained files to learn a bit about their names, content and location.

Afterwards look into the files extracted from the recovery program and copy kernel.image (remove the TI checksum from the end, if it exists) and filesystem.image to a combined file (as Freetz does with its own images while it builds the image to be uploaded to the device) and replace the kernel.image from the unpacked tarball with this new file.

Now you may pack the whole filesystem structure into your own, new tarball - which can be used with Freetz (use "Override options" to specify the location and checksum for the own image).

By the way ... why did you write your questions in this sub-forum instead of "Modifikationen -> Freetz", if your real interest is to get an image file, which can be used with Freetz? In my opinion, you should open a new thread in the right area for further questions or ask a board admin to move this one to the "Freetz" sub-forum. Many people using Freetz do not read all other questions, especially not in this place, which is more a sewer (in the sewerage) regarding nearly all questions around a FRITZ!Box device.