I'm absolutely new to this... I just wanna ask if it's possible to delete my domain ..for example after one year?( in case my business wouldn´t go well?)
Sure — just don't renew the domain (and set it to not automatically renew), and it'll expire when its time is up.
Or, another option for you would be to set up a cron job as well. But Not renewing is the easiest one since you don't have to do anything.