My friend, if you need to add payment via a bank card on your online store, then it would be best for you to contact Tranzzo for this service. They have been integrating various payment methods for online stores for a long time. Here is the link https://tranzzo.com/acquiring specifically for acquiring services.
Do you have any advice on what to give your friends for their new apartment?
I know such an online store, here is the link to it https://just-likewood.com/ and on it you can find similar products, just look carefully at their catalog. I bought a wooden 3D map of the USA with LED backlight from them. It hangs right above my bed in the room.
This is not a simple question and it is unlikely that you can find a simple answer to it. I recommend that you take your time and first read the information here and do this. I myself can say that I have similar questions for myself, and found quite a lot of information on the website at the link above. Therefore, I think that this link will be useful for you too.
Personally, I think that your friends gave you the right good advice, since Allegro is a very promising and smart trading platform. But even on it you need to know some nuances, for example, to succeed on Allegro you need to prepare theoretically, here you can read a little about it https://geschaft.pl/2022/09/22/i-sell-on-allegro/