First of all? You need to know the animation duration of your camera. If it is the default 100 frame, then you need to change the animation duration a little longer, such as 200 frames. If the frame rate is 25, your animation will take 8 seconds, which is not fast.

Second? After modifying the animation time, you need to enter the curve editor, find the path animation curve attribute of your camera, and move the second key back. (If not, you can delete your own camera animation and reset the camera path constraint animation, so that the duration of the new animation is 200 frames and 8 seconds. )

hope this helps ...