how can i down load movie from torrentz site

You need a bit torrent client.

I suggest to install qbittorrent from synaptic.

After you go to torrent sites or to torrent search engines and search what you like to download.

When you click the torrent file the qbittorrent opens it and start to download it.

Make sure you have enough free space to your drive for huge torrents.

after the down load movie any possibility in virus affect Ubuntu OS

If you want to check the file for viruses install an antivirus.

There is ClamAv and is open source.
Or there are manu linux free editions as Bitdefender or Avast.

thanks

Thanks demosthenesk, that solved my question.