The Spaniard joined the club in the summer of 2011 for £18m from Atletico Madrid, and has endured a mixed time since arriving at Old Trafford.
The Red Devils have been linked with a move for Stoke City goalkeeper Asmir Begovic at the end of the season, but De Gea believes that there is no need for a new stopper at the club.
"Of course when you arrive at a new club it is normal there will be low points. The important thing is to learn from them and improve," said De Gea.
"I know I am much better than when I first arrived at Manchester United."
United face Real Madrid in the Champions League on Wednesday night.