To realize 0 dB coupler or crossover, at first design 3 dB branchline coupler then connect two 3 dB branchline coupler in cascade but all the lines should have 50ohm impedance.
To design phase shifter, at first you need to calculate the line length to provide specific phase shift between input and output and then introduce bending. Means you need to design a bended microstrip line phase shifter.
I am sending some papers about butler matrix array, I hope these papers will help you to design the system.