There are several YouTube downloader apps that you can use and download all kinds of videos from YouTube for free cost. But you have to keep in mind that all the app is not legal. It is a third party app. Here are some top apps that you can use like: YT3 YouTube Downloader, YMusic, TubeMate, Telegram, Keepvid. For more detail you have to click: https://assistsuite.com/youtube-video-downloader-apps-for-android/