Nice video. The servo does move forward and back.
Not sure if you mean the fact that it is not moving at constant speed.
Anyway: you have to post the demo code you used in the video and the code that you wrote yourself.
You should post code by using code-tags
just three steps
- press Ctrl-T for autoformatting your code
- do a rightclick with the mouse and choose "copy for forum"
- paste clipboard into write-window of a posting
Servos should always be powered by an EXTRA Power-supply.
Servos pull too much current for the Arduino-onboard voltage-regulator.
Of course you can find tutorials and videos where the servo is powered through the arduino but this is near the limit and if you have a servo that pulls a little more current than the one shown your voltage-regulator will shutdown or burn through.
best regards Stefan