Don't use "C2" image, it's only for Odroid-C2 (as said in FAQ).
You probably have S905 box (not S905X), you need to use one of gxbb device trees, probably this one: gxbb_p200_1G_100M_RealtekWiFi.dtb
Hint: Android 5.0 on the box means S905, Android 6.0 or 7.x means S905X.
Bingo.
you are the best