United slumped to a disappointing seventh-placed finish in the top flight last term and have failed to win a competitive fixture under new manager Louis van Gaal this season.
However, the likes of Angel Di Maria, Radamel Falcao and Daley Blind arrived at Old Trafford before the closure of the transfer window as United look to kick-start their campaign.
Club legend Charlton is sure that United will turn the corner soon and is optimistic over Van Gaal's work in the transfer market.
"The manager is in charge of the team and in charge of the players, and he has given me and most of the fans some good news really and it is good news," he said. "We won't struggle anymore.
"We've started with some new players and we've not been playing well, but we will play well.
"I think that it's going to be a great adventure of how we pull ourselves round to get back to the way it used to be."
Charlton is aware that it could take time for the new signings to settle but is encouraged that some of the world's best players want to ply their trade for United.
He added: "I think it will [take time to adjust]. When you think of the players, the really great players that want to play for us, I feel really quite happy."
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