I can't install SuperSU because I get the "supersu failed to verify whole-file signature" error.
I figured the problem is caused by the fact that I don't have CWM or TWRP installed (rather just the stock recovery), but I can't seem to install them.
I've tried using Odin and also installing it directly from the Play Store according to their instructions.
In both cases, it gets installed but when I press Home + Volume Up + Power I still don't get to the CWM or TWRP recovery screens but just the usual old stock one.
What do I do??