The Bayern Munich forward was pleased with their performance against the defending champions but still sees plenty of room for improvement.
Thomas Muller has warned Germany against becoming arrogant after their thrilling Euro 2020 win over Portugal.
Germany laid down a marker by beating the 2016 winners 4-2 at Allianz Arena on Saturday, throwing Group F wide open.
Joachim Low’s side bounced back from a 1-0 loss to France in their opening game by seeing off Portugal in impressive fashion, but Muller says they cannot afford to get carried away.
Muller told reporters after the game: “We had a lot of good aspects, but also a lot of things that we still have to improve. That can cost points in the end.
“Now we have three points, now we’re good at it tournament and we have it in our own hands. Now we mustn’t overdo it or become arrogant – but we can believe in our quality. We can feel a little euphoria.”
Germany showed signs of promise during their defeat to France but few predicted they would be able to beat Portugal, who saw off Hungary 3-0 in their first group game, by such a clear margin.
After Cristiano Ronaldo tapped home from close range on 15 minutes following a breakaway, Germany regained their composure quickly and began pushing hard for an equaliser, eventually getting their reward when Ruben Dias turned a Robin Gosens cross into his own net.
Germany completed the turnaround before the interval thanks to another own goal, this time from Raphael Guerreiro, before racing into a 4-1 lead early in the second half thanks to close-range finishes from Kai Havertz and Gosens. Portugal pulled a goal back through Diogo Jota, but the hosts held on for a famous victory.
France are top of Group F on four points as it stands, despite having been held to a 1-1 draw by Hungary in their second fixture.
Les Bleus will be through to the round of 16 if they pick up at least a point from their final game against Portugal, while Germany will now fancy their chances of winning the pool as they come up against Hungary.