Video effect - slowmotion to fastmotion?
The term your looking for is called a speed ramp. There are lots of tutorials if you search for that.

Here are basic instructions for one way of doing that.


Right click on the clip in your timeline
Click 'Show Clip Keyframes' then 'Time Remapping' then 'Speed'
You can then add Keyframes and drag the line on your clip to alter the speed