thanks for your hints, finally I made the STACK/Maxima optimized, see pdf's below.
My short recipe:
In the STACK healthcheck, I first clicked on "Create Maxima image". Then I copied "Maxima shell command" (here
timeout --kill-after=10s 10s /var/moodledata_lms-ext/stack/maxima_opt_auto) into STACK's "Maxima command".
In STACK settting also I changed Platform type to "Linux (optimized)".