Hi @Desper,
There are different issues you have raised here. It is not clear to me what happened at the bank. From what you wrote, it seems you were both present at the bank and the bank gave this other person a loan in your name? I do not understand fully.
Regarding the other money you gave to your family member as a personal loan, there are various steps you can take. It is important to retain all proof you have of any money transfers and any written agreement you may have made about the loan.
You can write him a letter first simply requesting he repay the money. If there is no reaction on his part, you can send a formal demand letter (in German ‘Mahnung’). After this or alternatively, you can go to court to seek to get the money back. For this it is recommend to get legal advice.
Here is an article (originally in German, translated online to Portuguese) which gives a good overview of the possible steps:
https://***-advocado-de.translate.goog/ratgeber/inkassorecht-und-forderungseinzug/zahlungsverzug/geld-verliehen.html?_x_tr_sl=de&_x_tr_tl=pt&_x_tr_hl=en&_x_tr_pto=wapp
Best,
Éanna