Hey & welcome to GT!

Originally Posted by: jongjtjt

Whenever I let go of a string - I accidently play that string.

Effective muting technique will fix this. Use your picking/strumming hand palm to mute any & all strings that you don't want to ring. Use your fretting hand to mute also. When you are done fretting a string don't pull your fingers away from the strings. Continue to make slight contact with the strings. Just release enough pressure to stop the string from ringing. Keep enough pressure on the strings to stop them from making unwanted sound.

Also, remember if you are a beginner, then you are doing great just to get some notes fretted, picked & sounding good! Muting is another layer of technique to add in once you get the basics mechanics of fretting notes. Guitar is a constant process of refinement. Your scale in that video sounds good for a beginner. You just need to add muting to clean up the unwanted sound!

This tutorial covers fretting & strumming hand muting. In particular have a look at the beginner level tips.

https://www.guitartricks.com/tutorial.php?input=2281

I also cover basic right & left hand technique involving muting in this series of lessons.

https://www.guitartricks.com/lesson.php?input=10657&s_id=359

Hope this helps. Please ask more if necessary & best of success!