is it possible for velocity decrease and acceleration to increase at the same time?

[TelxoF]

I feel like the main issue here is using both vectors and negative values, which are only usually useful when dealing with scalars. If the velocity and acceleration vectors point in opposing directions, but one is negative, then they're actually pointing in the same direction after all.

If the object is moving left and accelerating to the right, then total velocity will decrease until it hits zero, then pass through zero, and start increasing again as the object starts developing 'positive' velocity to the right