Firmware FRITZ!Box Fon WLAN 7141?

Question

ADSL

I got the German adsl modem FRITZ! Box Fon WLAN 7141, the firmware in it is German, I couldn’t find English for this particular model (for 7140) ... I don’t need it as a modem, but it’s not realistic to sell it to someone without an English interface. So the thought came to me, but is it possible to flash it with something like DDWRT?
Inside there is such hardware:
Texas Instruments TNETD7200ZDW
RAM 32MB - Qimonda HY839SC256160FE-7
Flash 64Mb - SPANSION S29GL064A90TFIR3
WLAN - Texas Instruments TNETWI350A + TNETW3422
plus an unknown mikruha with an eplilon symbol and marking 3S250E
If possible, I would like to turn it into a regular Wi-Fi router: use the current lan-port as wan and distribute it via Wi-Fi. I would be grateful for any help (at least a link to a special forum where you can ask around)