I can't say Arda is a really good player for Real Madrid as long as he hasn't played a single game with his new club. He is just a talented young player discovered by Real Madrid scouts, but I am sure Arda will not easily break into the main squad if his performances are never better than some of the other experienced midfielders.
Indeed. We have no reason to claim whether he is suitable for Real Madrid or not, he still didn't play in any match for Real Madrid. Arda needs to prove his quality in some matches for Real Madrid. Although he is a very skillful player, it doesn't guarantee he will be suitable to play with Real Madrid main squad. But we also has no reason to claim he will fail as long as he didn't show it in any match.
Currently Real Madrid has many good midfielders to play with throughout the season, so competition between midfielders will result in young players being left on the bench. Brahim Diaz, Nico Paz, Jude Bellingham are good attacking midfielders for Real Madrid, so Arda Guller will definitely have to work hard to break into the main squad even if only as a substitute.
Of course, there are too many quality midfielders, it won't be easy to compete for the position in main lineup. But Arda can play as attackers, he doesn't need to rely on the position as a midfielder. I also think that Ancelotti will prefer to put Arda in attacking line. His skills is very needed to optimize for the chance of winning in the match.