Hi Akos,
welcome to Rune Audio.
turn on everything, start RuneAudio but under MPD I can not see DIGI+
Your DAC has to be enabled first, please see
here.
and a USB dongle.
USB flash drive or WIFI dongle?
and under network not a single wireless network is recognized.
Your Pi3 should work out of the box. The only thing to consider is, that it can not handle WIFI channels above 11.
Frank