Regarding long-term players, I think Erik ten Hag will do this in the summer transfer market, considering that today the winter transfer market has officially closed.
Buying players in winter transfer market is always more risky than in summer transfer market. Because after a winter transfer window, new players don't have weeks of training before playing first match for their clubs. With summer transfer window, after that, players will have many weeks for training and adaption in a new club before playing official matches for their clubs. Good performance in debut match is important to help new players have confidence and it can affect their later performance too.
Both manchester united and barcelona have shown epic performances this season and there is no doubt that the meeting between the two in the Europa League has been eagerly awaited by many football lovers around the world.
If either Manchester United or Barcelona win Europa League, they will have a good milestone in their rebuilding progress. It can be a solid foundation for their future in next few seasons.