Those people only trust these banks to hold their money, because they don't want to lose any of the value of their saving over the time. This is why Swiss banks could offer negative interest rate, because they're so trusted, and the demand is very high for their services, so they can just directly charge their cost with negative interest rate.
German bonds are pretty similar, Germany has a really good economy (on the long run), so people trust them enough to buy bond with negative interest rate because people speculate like the normal economies will fail, currencies (not EUR but the others) will lose a part of their value in a recession, so if you buy German bond even with negative interest rate will help them to preserve the value of their savings...
This is a signal for a coming recession or for a coming financial crisis... no one knows this for sure, but this is a signal...
I don't know if they are, but sounds like full reserve banks, where the entirety of your money is always there. Think bank vault instead. And this of course requires a fee for keeping that inside the vault without ever touching it until you want it back.
Most banks in the world do not do this, sadly they use fractional reserve, which is a form of legalized ponzi scheme, since they use your money for their interest, they pay you to give you an incentive to not withdraw your money...
Because if enough people withdraw their money, the bank has no way to respond, since the money isn't there anymore. At least not the whole of it, only a small "fraction". The only reason you don't see banks going bankrupt more often, is because they also came with the idea of a bank of banks that works with the same principle, called "The Central Bank". And to break that, a % of the population in that country would need to withdraw at the same time. But wait! they also made a World Bank just in case... which means... I hope you get it, if the world starts withdrawing, the bubble pops and everything collapses.
Which is why, it is wise for you to learn about the only school of economy that advocates the use of deflationary money, the Austrians: https://mises.org/books-library
Then you will understand where everything fits.
Should you get rid of your fiat for bitcoin or metals? Absolutely, leave in those Ponzi banks only the absolute minimum. It might not happen in your lifetime, but if it does, you will belong to the few that acted in advance and protected your funds by moving them away from fiat. You can also go with some more old fashioned assets like properties and such, but the main point remains: As little fiat as possible. Money in the bank is money at risk, think of a bank like an online wallet, very dangerous, could disappear tomorrow without warning (and yes, banks have gone before, leaving the people without their money).
But of course they want you to depend on them, their life depends on it...