Yes, almost all EU law that was in force at the time of exit was kept (and is known as "retained EU law"), with necessary modifications. For the GDPR specifica

Yes, almost all EU law that was in force at the time of exit was kept (and is known as "retained EU law"), with necessary modifications. For the GDPR specifically, the UK basically forked it and has what's known as the "UK GDPR". They basically just gave the powers that lie with the Commission to the Secretary of State and deleted the bits that dealt with cross-border collaboration between DPAs.