While we don't have a feature for slowing down video built into Shakr, it's possible to accomplish this using a free 3rd party software, such as iMovie or Windows 10 Photos app.

iMovie
https://support.apple.com/kb/PH22933?locale=en

Windows 10 Photos app
https://mspoweruser.com/easily-make-slow-motion-videos-windows-10-photos-app/

Please keep in mind that if you slow down the video too much, the audio will become distorted.