Ambrosius joined the Hamburger SV youth academy in 2012, rising through the ranks and making his professional debut in the Bundesliga in March 2018.

[10] In the first half of the new season, he was behind Rick van Drongelen, David Bates and Léo Lacroix in the depth chart, and neither under Titz nor under his successor Hannes Wolf he made an appearance in the 2.

In February 2020, Ambrosius returned to first-team practice as Gideon Jung was utilised in defensive midfield following the injury of Adrian Fein and only Ewerton was available alongside central defenders Rick van Drongelen and Timo Letschert.

[13] After Jung received a red card on 29 February against Erzgebirge Aue and Ewerton suffered a long-term injury, Ambrosius was included in the first-team squad for the matchup against SSV Jahn Regensburg on 7 March for the first time that season.

At the beginning of the 2020–21 season, Ambrosius became a regular starter under new head coach Daniel Thioune and formed a duo at centre-back alongside new addition Toni Leistner.

[23] On 21 June 2024, Ambrosius joined Swiss Super League side St. Gallen on a free transfer, signing a three-year deal.

Due to numerous cancellations in his playing position by Nico Schlotterbeck and Maxim Leitsch, Ambrosius was called-up by Germany under-21 coach Stefan Kuntz in early October 2020.

[25] However, as Ambrosius tested positive for SARS-CoV-2, he was unable to participate in the 2021 UEFA European Under-21 Championship qualification matches against Moldova and Bosnia and Herzegovina.

In July 2022, the president of the Ghana FA, Kurt Okraku, announced that Ambrosius was one of the few players that had officially switched allegiances to represent the Ghanaian senior national team internationally.