The easiest and most direct way to download YouTube videos is to use an online parsing download tool.
You can use it by opening your browser directly.
The most common parsing tool I use is "DLPanda".
Directly Google search "Youtube video downloader dlpanda" and you will see this online download site.
Step 1: Open this DLPanda site.
Step 2: Paste in the link of the video you want to download.
Step 3: Click the download button.
Step 4: Select the desired video (audio) format and click to open the video, then click on the option to download in the bottom right corner.
This is done.
Tip: Video and audio are separate and need to be merged by yourself.