Joao Neves and Martin Martin Zubimendi are defensive midfielders who have been linked with Manchester United. These players have attracted the attention of several clubs so if Man United are interested they must immediately make a deal, the club really needs to look for better players than last season to improve next season's performance because Casemiro's performance continues to decline and Man United cannot continue to rely on him.

Leverkusen defender Jonathan Tah has also been linked with Manchester United. He guarded Leverkusen's defensive wall last season and yes, Man United needs strong back line players, because last season Man United's defense was too weak, the club must be able to make a good offer to Leverkusen to releas this player

Source : Jonathan Tah-MU
If Man United has made a lot of improvements I believe their performance will improve but if they keep the existing players like last season I'm not sure Man United will perform well next season (IMO).