How woulc you answer your own question if someone else asked you the same? 
You shared a final state, but nothing about how you got there so there is no way to point out what you did wrong. If th filesystem is read-only, that means there is no way to write that filesystem regardless of what permissions you try to set. It is not about file permissions at all.
Please, share more about what you did exactly to get this error and share configuration files and commands, everything that can be shared publicly. Please, don’t forget to format your inserted source codes: How to format your forum posts