My problem is that I'm 16 and can only deduct 50 euro per week at the machine. But I would now like to order a laptop online with online banking for 210 euro, would it then work or does this "rule" also apply to online banking?
It is so that you have to go to the bank if you want to increase the limit.
For 16 years the amount you want to buy is probably too high anyway and the order is rejected
In addition, no one knows your contract data and does not know what online limit you have at the bank
There's a reason that "only" 50 euro a month can be "deducted". At 16 you are not yet fully capable of doing business and can only do business in the amount of the "pocket money paragraph". Typically, no dealer will engage in a transaction with a minor without the consent and signature of their legal guardians. There are also legal reasons for this. If there's a minor, the money can't be collected in case of doubt. So the parents have to be involved for better or worse.