There is useful pyhton library that can fast download Youtube Video in simple trick. You just only need to paste link that video.

First of All, make sure your system had installed python, mine python3. Then pip3. If this pip3 not installed, just hit this command on your terminal:
sudo apt-get -y install python3-pip

After that, install pytube library with this two lines:
pip3 install pytube
pip3 install git+https://github.com/Zeecka/pytube@fix_1060#egg=pytube
# patch

the second line must be executed to avoide error like this:

PYTube Error
PYTube Error

Now, just hit on terminal with this syntax: pytube [url], for example:
pytube3 https://www.youtube.com/watch?v=fNsyaEL7_SA
Loading video…
WOW!!! Ini Dia Perhitungan Super Cepat Validasi Metode (VMA) Secara Spektrofotometri UV-VIS.mp4 | 30 MB

Using Script:
create new py file, paste code like this.
import pytube
link = input(“URL target: “)
pytube.YouTube(link).streams.get_highest_resolution().download(‘Videos/’)

Where Videos is folder to save file.
Cheers.