So, it is a foreign country.
If I may be so bold. I started studying electricity and electronics in 1975. Went to college for a while with a major in electrical engineering but never finished. I have done electrical work since 1983 and have a fat and juicy license.
Ned to break it down into 2 problems.
Here is how a GFCI outlet works. If the current load on the neutral (white screw) changes .03 percent or greater in a certain amount of time, it will trip. This is why it has been acceptable to update an old house that did not have grounding conductors in the "romex" to be safe. Because it doesn't trip on current to ground, it trips on current change on the neutral.
But this can happen with moisture providing contact between the ground and neutral. In fact, the poor electrician's GFCI tester, if he does not have a smart plug with him, is a piece of "insulated" wire to push into the ground hole and the neutral (longer) slot.
Another important thing that must be done is to have in-use covers on outside outlets. This allows having a cord plugged in without exposing the outlets to rain.
Also, outlets installed outside should be weather resistant / tamper resistant. They have membranes that ward off rain when a cord cap is not plugged in.
Extension cords are likely culprits. Also, some mosquito zappers and misters can be a problem because they (especially the old ones) use a buck and boost transformer where line and load side neutral are common to each other.
It is also not uncommon to have a GFCI in the garage that controls exterior outlets. It is also not uncommon to have a separate garage circuit but not always.
It is also common for people to plug a beer fridge into this when it would be better with its own circuit.
It is not modernly common to have master bath circuit on with the garage. These days, that would fail inspection.
And sometimes, breakers just wear out.
You have a Siemens panel. Technically, it will take Siemens, Homeline, and Cutler Hammer BR. But Siemens will fit in the dead front (front plate you see around the breakers.)
How long ago did this electrician do the work? I ask because without company, we have a 1 year warranty from the date of installation on parts and installation, excluding light bulbs.
So, if he did an incorrect job or one his connections came looks and now you have a hot touching ground, which would cause the breaker to trip, then he should warranty his own work.
Also, just to make sure, to reset a breaker, turn it all the way off until you feel a click. Then on until you feel a click again.
We tend to run into these problems only on days that end in the letter 'y'.
And many is the time we have had to correct the wiring of a GFCI that others installed.
So, unplug everything from the circuit. Like the other guy said, it is a process of elimination.
But the advantage to hiring another electrician (insured and licensed) is that your insurance company will not fault you if the house gets damage from an electrical fire. Especially from electrical repair work. If something happens, you refer the insurance company to the electric contractor you hired and they talk with their insurance people.