Smooth slider that smoothly controls video timeline position

It's not the same. I want to achieve certain flexibility in creating interaction. Storyline is very limited in that manner because of it's simplicity for the user. In the other hand, advanced users can't achieve a lot of things. In this example, I wanted a user to move a point on a graph. When he put the point on certain place and clicks submit, I can evaluate where the point is and give him a feedback. For example, if the point is on a function minimum, I can explain a minimum, but when he moves it to functions maximum, I can explain the maximum. I know Geogebra is beter for math stuff, but since I create content for lot of different topics, I always want to experiment with interactions mechanics. So I decided to try with video displaying graph and point that moves along the line throughout the video. 
To make a proof of concept I sniched a free video from Pixaby just to try out the mechanism of moving video back and forth with the slider. Results are so-so, as you can see. If I only had some javascript info about video and other objects, that would be easy peasy.