What should I look for when buying used One X?

you should be able to buy everything with points - when you want to buy a full game just look at the bottom of the screen and select "buy with points" I think it is X button you need to press.

When it tells you that you need another car,click your x button to see the restrictions.You should be able to buy one once you know what you need.

what you're looking for is a split transaction. to do it though you must have a card or paypal on the account, click on the item you want to buy and confirm the purchase a message should appear and say "Hey you have X amount on your MSA would you like to
use that first?" yes than it will charge the rest on the card. But I usually prefer using currency anyways since it's a lot easier. Oh and yes do this on the console when you go to buy it.

Where can I buy a new Xbox one x power adapter online or in Berlin?

Hello LarsSchimmelpfennig

here, The Xbox one x has an internal power supply what you are looking for is a cable i would suggest buying one of amazon This link should take you to the product https://www.amazon.com/gp/product/B...8f213ef368b&pf_rd_r=2JMM48E839V90QYV42H5&th=1
Since you suggested the topic of berlin i am maybe realizing that you might be talking about a wall outlet adapter in this case i suggest doing some research on where you will stay and what type of outlet is used there and buy the product now.

its just a prototype look at what the xbox one x look like when it was leak as one compared to what it looks like now