[Q] Can't edit in es explorer/super manager - only readable - help! topic

Hello ppl's have looked everywhere online for someone whit the same problem as me but whit out luck so now I am crying out for help!

I have a problem i don't know how to solve, I have a Samsung Galaxy Note Pro 12.2 and I want to disable to button's (the return and the task bar button) I have found a couple of guides that all lead to the same conclusion
Which is: I need to write/edit in a script called "Generic.kl" located /system/usr/keylayout/Generic.kl
The problem is that when I rewrite/edit the script it comes whit an error "/system/usr/keylayout/Generic.kl: open failed: EROFS (Read-only file system)"

I have a custom ROM called hyperdrive installed
My device is rooted whit superSU and ES File Explorer have # (super user permission)
I have enabled ROOT Explorer, pressed it and mounted R/W set all to R/W after that in propperties change the file so that it say r/w under every domain

It diddent work whit ES Explorer so I tried Super Manager

My device is rooted whit superSU and Super Manager have # (super user permission)
I have enabled ROOT function and in propperties change the file so that it say r/w

I have spent a lot of time looking for a solution and I'm a sek away from giving up..
So there it is hope that there is someone able and willing to help me whit my problem