Is it true that the Boeing 747 has a faster speed than the airbus a380?

Yes. The maximum cruising speed of the Boeing 747-400 and Boeing 747-8 is Mach 0.92

(614 mph, 988 km/h, 533 kn), which is faster compared to the Airbus A380-800 which has a maximum cruise speed of Mach 0.89 (945 km/h, 587 mph, 510 knots).