The Red Devils have taken just five points from their first five games under the Dutchman and let a 3-1 lead slip as they lost 5-3 at Leicester City on Sunday.
However, the former Bayern Munich boss is confident that he will be able to reverse the club’s fortunes in the coming weeks.
“At this moment this is maybe my toughest job but we have to see in a year,” Van Gaal said.
“We cannot say it about one week with the injuries. As a manager you know already in advance that it’s a big challenge.
“This club is in a transition. What you don’t know in advance is what the hard moments will be. At the start we won all of our games but now we are in difficult circumstances.
“We should have won last weekend [against Leicester City]. We had to win when we were 3-1 up. If we had we would have been two points off second place, but because of the loss you are now questioning me.
“If we won then it would have been different. We will overcome things – the season lasts a long time.”
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