My reason for getting a credit card as soon as possible when I moved to Germany, was being able to switch the country of residence of some of my services to Germany, because they only accepted a local credit card as proof of residence here. Google was the main culprit in this regard. Mind you, the credit card itself is a serious joke - it's designed to be useless as far as I'm concerned. You cannot change the billing date, the app doesn't even show you the cutoff date. You cannot change the pin at all - if you request a new pin, they send you a new card.

The only good way I've found to use the card is through Paypal, ironically. At least this way I can see, down to the minute, what I spent and where, which the bank is unable or unwilling to show me.

There is no credit on the cards you get in the EU, except if you ask for some. By default there is no.

A credit card is, well, a credit with rates etc. You may pay a part and the rest runs as a credit. You have a specific contact for that. Also a credit card can be issues without a backing bank account. Our cards always (in practical sense) are backed by an account.

This is not how the cards work in the EU. You have delayed debit but no credit (formally - in practice you spend the money of the bank obviously, but you have to pay in full after 30-45 days).

American Express is a system that is used by companies (for various reasons) and this IS a credit card, but people use it for business related reasons and its delivery is triggered by the company.