With respect, I do agree with the other poster that there appears to be something you are doing that is causing the battery to bloat, something you might not even be aware of/at fault for that is causing the battery to become damaged.
This battery technology is not unique to Apple, lithium polymer is a common battery form used by dozens of other products and companies, and bloating is quite rare. It is possible that you are causing it without intentionally doing so, for example, the current flow in your area might be inconsistent, causing damage to the cells in the battery. It might also have spikes in the grid that small electronics can't handle well. There are many unknowns here, and while Hungary is not a 3rd-world nation like sub-saharan Africa or other places, it is not France. I think you might find value from having the lines in your home checked and verified over a one week period to confirm that the electric flow is stable, consistent and not prone to spikes, low/high amplitudes, etc.