You can slow down a video clip in the Time-Line mode by selecting that video so that it is highlighted orange, then go to the Effects tab and select Video Effects, from there find the Speed section, You can see a slide bar for the speed section, moving left slows down, right speeds up, and there is a tic box for reversing the video.
Thank you for your detailed answer as it helps me. I'm reasonably new at this.I followed it step by step & it worked fine. There is so much to learn but the effort is worth it.