Main Breaker Gets tripped every 1-2 hours but last longer in the night
When an appliance has an internal shorting or arcing fault, or electrical wiring has is shorting hot or neutral to ground, that is called a "ground fault".

You have a "Whole-house RCD" - aka GFCI - it looks for current leakage from ground faults. SOP in Europe-influenced electrical installations is to fit a 30-35ma (milliamp) RCD that protects the whole house.  The goal is to protect the house from arcing fires; 30ma can kill you.   This unit is typically combined with the main circuit breaker. 

Beyond the whole-house RCD, you then have branch circuits with circuit breakers. Most of them will be one size such as 13 amp or 16 amp. Take note of that. 

North American practice is to protect each branch circuit with its own GFCI (RCD) device (breaker).  The goal here is personnel protection, so only bathrooms, kitchens etc., and a lower detection threshold of 8ma.  

My suggestion is to do the American thing - and replace one of your branch circuit breakers with an 8ma personnel-grade RCD, of the amperage rating of most of your branch circuit breakers.  This will have a lower threshold than the main, so it "should" trip sooner.  If the problem is on that branch, the trips will mostly now occur on this breaker.  If that branch circuit is not the problem, then swap the breaker to another branch circuit, and try it again.  Eventually you will narrow it to a single branch. 

Then unplug all the appliances and test again.  If that does not clear the problem, then disassemble all the junction boxes in that branch and look at the wiring.   If unplugging the appliances does clear it, then return one appliance a day and when the problem returns, that's the one.  Have the appliance serviced. 

This method won't work for the few odd-sized breakers you may have for stove, water heater, air conditioning, etc.  Simply switch those off for a day (when feasible) and see if the problem goes away when they are off.