I would like to buy an xbox one around 230 euro with how many years one may buy that?
If your parents agree
There's actually no age limit on buying when there's no age limit on the console (for example, in a bundle). From the age of seventeen, you have limited legal capacity and from 18 then full legal capacity.
Your parents can theoretically make a retrospective mistake, but you can buy it.
From 18, before until you have limited legal capacity - and a console purchase for this price is regularly no longer under the pocket money paragraphs. Otherwise, parents can veto a former if they disagree with the use of such devices.