That app uses external apps to do a lot of things
Like video playback calls out Players to playback what you want to watch, Like VLC, EXO,MX
But you have to have these player apps actually installed on the device in order for them to work. The app doesn't give a way for you to install them yourself
I think the same thing applies to this Advanced download manager
I searched for it on Google Play and its not there, so I am really not sure where its from
Sounds like a rabbit hole mission to find this
I will forewarn you though about downloading movies etc from apps like BeeTV
A lot of times they just stream torrents, and if you download torrents without a VPN. ISPs will report Copyright infringement notices and warn you
In Canada its simply just a warning letter, but in America its been known for movie studios to sue people for torrents.