The ?18.9 million ($29.8 million; 22.7 million euros) signing was dropped by Sir Alex Ferguson after the surprise 3-2 home defeat to struggling Blackburn on December 31.
But De Gea insists he is finally coming to terms with the Premier League after helping United keep their title challenge alive since returning to the starting line-up.
The 21-year-old Spaniard also kept a clean sheet in Amsterdam last month in the Europa League first leg victory over Ajax before United went on to advance 3-2 on aggregate.
They face Athletic Bilbao at Old Trafford on Thursday in the last-16 first leg, a match De Gea is eager to do well in.
"Athletic are a good team. I've got lots of friends there and it'll be great to go back to Spain (in the second leg) - and to win," he said.
Speaking about his tough start in England, De Gea added: "Honestly, I think I have done more good things than bad things, but perhaps what I have done wrong has been reported on more.
"I have done very good things. I am happy with my performances to date and I am sure there is more coming.
"Of course I am self-critical. I have to be. Any footballer must learn from his mistakes to improve day after day and know what his weaknesses are."
De Gea said his team-mates have helped him settle at Old Trafford.
"Every morning I enter the dressing room and I see (Ryan) Giggs and (Paul) Scholes. It is like I am dreaming. I am proud to play alongside them.
"I see Giggs improve every day. I tell him 'I am next to be a football legend'.
"I have a good relationship with most of the players, but especially with those who speak Spanish."
United warmed up for Bilbao with a clinical 3-1 win at third-placed Tottenham on Sunday to move to within two points of leaders Manchester City.
But the Spanish visitors will be encouraged by United's stuttering form at home in Europe this season.
They have won just once in four European games at Old Trafford, and lost 2-1 to Ajax last month but still advanced on aggregate.
Defender Chris Smalling should return to the line-up after a recent head injury, while Brazilian midfielder Anderson's presence on the substitutes bench at Tottenham proves he is also fit again after a knee injury.
The game is likely to come too soon for both midfielder Tom Cleverley and Antonio Valencia, although the winger could feature in the return leg next week.
Bilbao, fifth in La Liga, arrive in Manchester on the back of a 2-0 win over Real Sociedad.
They are expected to travel with a full squad, albeit shorn of long-term injured absentees Aitor Ocio, Carlos Gurpegui and Xabier Castillo.
"Playing against Manchester United is not like any other game," said Bilbao manager Marcelo Bielsa.
Source: AFP
Source: AFP