It is not a "main breaker". It is an RCD that was added after. As it only provides protection for the two 20A (not 40A) power circuits there will be a main breaker (which covers all circuits) somewhere else.OK. I see the text underneath now. But this is a single pole mains breaker. Two 40A and a 32A on the same circuit still draws more than the rated capacity of 63A (possible 72A). Regardless of the theoretical load capabilities of the circuit there is obviously a heavy load on the 2 x 20A circuits such that adding in the extra 32A is overloading the main breaker. The single pole main breaker in this case needs to be 80A minimum. It would be good to see the whole picture regarding this circuit layout as that one picture doesn't tell the whole story. Turn off the two 20A circuits and run the 32A alone just as a quick test. If the breaker trips its an earth leakage issue. If it works fine then it is an overload issue requiring a larger main breaker. Easy test.
The problem here is the electrician should NOT have wired the new 32A circuit through that RCD. He should have installed a separate breaker and RCD in one for the dedicated circuit.