In the end, it didn't worked out fine. For each time you switch on your controller, you'll need to install the FLY app.
I found someone who helped me installing the software (remotely) and now it works perfect including the FLY app that remains...
Thanks! I'll keep on searching and when I found the solution, I'll post it here for any future user experiencing the same. Again, thanks for your help!
Oke I made so progress.
I downloaded firmware for the RM510B (latest version) from the following website
Dank Drone Downloader - Web App
Then I used the the old Drone-hack application (1.37) to upload the firmware to the controller.
After...