Van Gaal, who replaced the sacked David Moyes in the off-season, has claimed just eight points from six Premier League games, while he also oversaw a humiliating 4-0 defeat to MK Dons in the Capital One Cup.
The 63-year-old, though, remains confident in his abilities and has no doubt he will realise his ambitions in England.
"I didn't have to come here to Manchester United. They asked me," he told national newspapers.
"And I will take United back into the Champions League yes, but not at once.
"There is a trajectory and a process of three years. I have signed a three-year contract. Believe me, I shall finish that."
Meanwhile, the former Netherlands, Barcelona and Bayern Munich boss admitted his squad lacks some leadership following the departure of senior campaigners like ex-skipper Nemanja Vidic and Rio Ferdinand.
"At the time I was coming to the club, big leaders were leaving - (Patrice) Evra, (Nemanja) Vidic, (Rio) Ferdinand," he said. "They were big leaders.
"Also, leadership is a process - you don't go from one day to the next and become a leader.
"It's a process and now a lot of players are in that process."