If you love to play volleyball and are looking for something different to do during summer in Luxembourg, I can recommend you to join a Beach Volleyball tournament. At the moment I know there are two in Luxembourg: The Luxembourg Beach Open and the Beach Days.
Both of them are very different, so it depends on how good you are/ or how professional the team players of your team are. In The Beach Open, normally are very good players, and many teams have professional volleyball players. The teams are more organized and the majority have uniforms or are sponsored by companies. On the Beach Days, it is more informal, where people just go to have fun and are not really good at the sport, in fact they don’t let more than 2 team members be professional players.
As you can imagine, I am not at all a professional volleyball player, so I of course attended the Beach Days tournament with several friends, we were in total 25 people so we made several teams. This event is very fun because you can be the whole day at the “beach” (sand) having a nice time with your friends and playing from time to time. There are drinks and food served all day and at the end there is a party. The only problem is that normally the event is on Sunday, so if you have to wake up early on Monday morning staying late for the party could not be the best idea.