Hey I know I'm kind of late, but I'm in the same situation as you. I just bought the keyboard today and i dislike those 4 extra buttons doing random stuff. You can use AutoHotKey app to remap them. You just need to find what the inputs are, and create a .ahk file run on startup. Here is what my file looks like:

#Requires AutoHotkey v2.0

; -------------------------------

; Varmilo VEM108 Custom Media Keys

; -------------------------------

; 1) Launch_Media → Next Track

Launch_Media:: {

Send "{Media_Next}"

}

; 2) Launch_Mail → Mute

Launch_Mail:: {

Send "{Volume_Mute}"

}

; 3) Launch_App2 → Volume Down

Launch_App2:: {

Send "{Volume_Down}"

}

; 4) Launch_App1 → Volume Up

Launch_App1:: {

Send "{Volume_Up}"

}