In the Spanish La Liga this season Barcelona are seem to be invisible subjugating Real Madrid to nothing I have never really season in all their rival seasons in the league. Madrid couldn't even get a point in their four clashes this season and that's very much of a poor head-to-head for a club that bought one of the most expensive player in the world. I think Real Madrid would need to buy a natural top 9 (to allow Mbappe play in normal position) and also strengthen their defense too if they want to stand tall against Barcelona next season.
Real Madrid don’t need to sign anymore forward or natural no 9, they have Endrick and even Mbappe who says he likes to play from the wings. He’s been prolific this season in front of goal, Endrick has also shown what he could do with the little opportunity he’s given. What Madrid needs to sign is an additional center back and right back tho heard Trent Alexander Arnold is coming and they also need to give opportunities to youngsters and trust them. Endrick is proper no. 9 or a natural like you said, he’s quality.
Then they Settle the Vinicius and Mbappe problem, their team spirit is low they need to up that a lot cos sometimes it’s like everybody plays for himself no communication no cohesion, sometimes they even fight for the same ball like bunch of inexperienced girls in my hometown playing football.
Bunch of inexperienced girls!

please don't make me laugh out loud.
Seriously, all what Real Madrid need is a player that's a natural top 9 and if Endrick can deliver on it as expected then it's better, because with a natural striker on the pitch Mbappe would have to play from the flank since he can score with both foot he can play on any side of the wing with Vino junior on the other side while Endrick is positioned as forward with Bellingham sitting deep behind like a false 9 . It would create more balance and good communication in their game than the individual football they play on the pitch under Ancelotti which really hasn't helped this season.
Meanwhile on the aspect of defense, they really need to add new legs to reinforce their backline against the cheap goals they do concede in this season. I want to believe that when Xabi Alonso arrives he would know what right changes is needed to be put in place to bring Madrid back on track for el classico's.