I tried to use my volumio rasberry on wifi with edermax wifi dongle
but language gets mixed up and is shown in config file like text
resetting the language to Dutch fixed it, but after reboot it returned to these mixed text
second question why is volumio ui responding extremely slow when using wifi ?
Sorry, can you clarify what you mean here … “but language gets mixed up and is shown in config file like text
resetting the language to Dutch fixed it, but after reboot it returned to these mixed text”
To your second question, are you saying that your wireless speed should be comparable with the wired connection speed? Perhaps, it is just that your device is too far from the AP/router.
Can you refresh the page?
if you look on the bottom of the image you’ll see that the sub menu’s are tilted
COMMON.TAB_BROWSE , COMMON.TAB_PLAYBACK, COMMON.TAB_QUEUE
thats not “common” English and it’s certainly no Dutch 
second issue:
I joined volumio to my 2,4Ghz SID APMM with a different ip on wlan0 from my lan device eth0
opening the ui on the LAN ip , it is responded as it should
the ui with the wifi ip it is very slow and does not want to load pages at all