In Danish you say (to one person) " Du skal 'swømme' nu" - (to more than one) "I skal svømme nu". if you use the word "skal" is is the same as ordering someone to swim, if you ask someone to swim use the word "må" or "kan"
Thanks a lot kllun for your suggestions. I know you want to help me, but I'll keep my translation the way it is. I think it's ok this way. But don't hesitate to give me other suggestions. Help is always appreciated.