I am trying to replace a light fitting but when I switch on the electric the circuit breaker cuts out the light switches, I have connected everything as the instructions say what am I doing wrong,

2 black wires (existing) to 5 blue wires (new light)
2 red wires to 5 brown wires
2 earth wires to 1 earth wire

The Brown is live and cannot be switched to the Blue wire.
The fixture should have a blue and whichever wire is coming off switch.
I think you are switching live to your return.
Does Breaker trip when switches are off?