Guild Wars 2

I would like to know if thas legal in game politics, to buy an acc from a player that stopped playing.
and if there is a way to do it safely, in other games you can switch the acc email for example. but dont seen thats how to do it here.

Imma hazard a wild guess and go with that being majorly against the rules. And I am sure that even if anet is ambivalent about it, they certainly arent going to offer any support to assist you in giving anybody besides them the purchase price for the game. I wouldnt pursue it if I were you. Sounds like a splendid way to get banned to me.

Form the Guildwars 2 User agreement:

’
(b) Each Account may only be used by one person. If a minor has been allowed access to an Account by his/her parents or legal guardians, only that minor may use the Account thereafter. You may not make any assignment or transfer of rights, obligations or liabilities related to this agreement and any attempt by You to do so is null and void. However, You may allow access to an Account to any family member who is living in Your household.
’
(source: https://www.guildwars2.com/en/legal/guild-wars-2-user-agreement/ )

So in other words it is not allowed. Besides that taking over someones account is risky at best. The first user has knowledge of the gamekey and has proof that he bought it. Those are the things needed to regain access after being hacked. So in theory, the original owner can reclaim the account anytime and you end up with nothing.