Ruwen played first international in 2002. He's a modern defender, so he uses long pips and an attacking rubber on the forehand. At the European Championships for youth he reached the first place together with the team. In 2003 he won even gold in the singles and with the team, so he climbs from place 90 in the world rankings for adults to place 70. Since 2005 he played different tournaments, for example the World Junior Circuit, where Filus reached the Quarterfinal. At the World Championships he came under the best eight players in the doubles. His first tournament at the Pro Tour end with the reaching of the last 64. 2006 Filus won bronze at the European Championships for youth, with the team he won gold. Since 2007 he played in the adult area, too, where he reached the Round of tha last 16 at the Korea Open. 2008 he played some Pro Tour tournaments, since 2009 he played different events, for example the European Championships, where Ruwen came under the top eight, he lost to Timo Boll. 2010 he played only two events, so he fell back to place 60 in the world rankings. 2011 Ruwen played at the World Cup, there he won bronze together with the team. At the WTTC he came under the last 64 in the singles. At the European Championships he won gold with the team. 2012 he came under the last 16 at the ETTC, on the Pro Tour he won the Czech Open. 2013 he won bronze at the Czech Open and came to the Quarterfinal at the ETTC. 2014 he had very strong injuries, but in 2015 he reached the Quarterfinal at the ETTC again, with the team he won silver. 2016 the German team lost in the group qualification. 2017 he won gold with the German team at the ETTC, 2018 was it silver at the WTTC.