Did a little research a couple articles say Dortmund did extend his contract by 2 years until 2025.
no official announcement from Dortmund about the extension,
also a couple of articles state that Dortmund do not want to sell him this summer but then in the same articles it says Dortmund would want more than 100 million euros.
Then another article that came out in March states that Dortmund want to extend his contract but Bellingham wants a release clause inserted in any new contract with Dortmund.