It’s confusing the taz asked the responsible authorities. The important part is the update at the end:

An earlier version stated that the BMI [Federal Ministry for Interior] and the Berlin police had confirmed the ban to the taz. The police had initially referred the taz to the BMI, the BMI to the Berlin Senate Department of the Interior. However, neither had initially denied that Varoufakis had been banned. A spokeswoman for the Berlin Interior Administration responded to a corresponding query on Saturday evening, stating that a ban on Mr. Varoufakis had not been issued by the LEA (State Office for Immigration) as a subordinate authority of the Senate Department for Interior and Sport. (Translated with deepl.)