So basically sometimes my rear right door won't open ( unlock) I  can open it from inside but not from outside ... and sometimes it works perfectly  ( it didn't work for  2 weeks and then worked for 2 months)  I wood  like to know if somebody had that experience  and how did you fix it

If it works some of the time, then try and spray some lubricant (WD40) on the actuator.  It might be stiff and not moving easily

 

If problem continues then you need a replacement lock motor

 

 

Maybe this will help

 

well I found out all I needed to do is change key battery  

I find that weird, I would have thought the key would have told the car to unlock the doors based on the settings, but it would seem the key tells each door to unlock and obviously runs out of oomph by the 4th door