The data on the NewBanking platform is completely owned by the account of the individual that uploaded the data.
Data shared through an access on the NewBanking platform is still owned by the individual that shared the data. This individual can always revoke their access, which will notify the company to delete the data.
Note that companies are sometimes required by laws such as the Anti-Money Laundering law (AML) and bookkeeping laws to store data even after a business relationship is over. Such information can also be stored in the NewBanking system, which then supports automated deleted when the legal storage requirement is over. This is no different than any other system operating in such regulatory environments.
Furthermore, all data is stored within the EU and are fully encrypted with 256 bit encryption.