If the wattage of your 3,500 kWh PLN connection is sufficient for your household, and an MCB with a higher value is still installed, this probably indicates a problem with your mains voltage. This bigger MCB is a workaround from PLN that is easier to implement than the necessary upgrade of the electricity grid.If I understand correctly, we will upgrade the fuse to a higher amp rating but the same wattage.
I recommend measuring your mains voltage. Do this several times a day to get a better picture. You can easily do this yourself if you have a prepaid meter. Press 41 and <enter> on the meter, and it will show the real-time mains voltage value. This should be around 220V. If the voltage is very low, it can be harmful to your household appliances, and you may consider a voltage stabilizer in this case.