Brøndby On 17 May 2022, Schwartau signed a three-year contract with
Brøndby IF which tied him to the club until the summer 2025. He was officially promoted to the first team during 2022–23 pre-season and assigned the number 41 jersey. He made his professional debut on 17 July 2022 in the season opener of the
Danish Superliga against
AGF at the age of 16 years and 61 days. In doing so, he became the youngest player in club history and also became the first player born in 2006 to make an appearance in the Danish Superliga. On 14 August, he scored his first goal in a 2–0 win against
OB becoming the club's youngest league goalscorer, and second-youngest overall in Danish Superliga.
Norwich City On 24 August 2024, English
Championship club
Norwich City signed Schwartau on a four-year deal with a club option of an extra year. The fee was undisclosed, but reported to be £2 million with Brøndby retaining a 15% sell-on clause. He scored his first goal for the club on 26 December 2024 against
Millwall at
Carrow Road. At the end of Norwich City's
2025–26 season, Schwartau was named as the young player of the season. ==International career==