Question

How can velocity change even if speed stays the same

Answer 1

A car traveling in a straight line at a constant speed has a constant velocity, but if the car turns around a curve in the road then the velocity changes, even if the speed stays the same. Or a car that is changing in speed, even if it continues in the same direction, has a changing velocity.

Answer 2

"Velocity" is made of the speed and the direction of motion.  So if the direction changes, the velocity changes, even if the speed stays the same.

Examples:

-- an object traveling in any closed path, like a roulette ball, or an orbiting satellite;

-- a car turning a corner at a constant speed;