YouTube has a vast number of free tennis coaching videos, here are a few samples from some of the best tennis academies. You can visit the YouTube sites to get many more. You can just 'Subscribe' to each site and click on the bell icon to get a notification of new videos loaded onto that YouTube site.

Top Ten Doubles Strategies https://youtu.be/g9RZnnApDi8 from 2minutetennis

How to develop your one handed backhand  https://youtu.be/r6Yr4HDGtdM Tom Avery Tennis

Maximum forehand topspin https://youtu.be/AQvD_pMVL8E EssentialTennis.com

Forehand Volley https://youtu.be/JG0CBb82Pe8 PlayYourCourt

Fixing your serve ball toss https://youtu.be/HsnXfnsy3C8 Total Tennis Domination