disable download video

Rod is right, of course. The only way to prevent easy 'download and save' is by putting your video on a streaming service. YouTube works well too. Setup a 'private' account on either so the video isn't publically searchable/visible. Also check the provider's terms if you have any such concerns.

Or you can go with a paid, professional service like Kaltura, BrightSpace, Panopto, etc. It costs but you have no ownership or control issues.

Or you could do it yourself if you have a server with solid bandwidth out - there are a few open source streaming video packages (i.e. Red5).

Put your video on an MP4 streaming service provider such as Vimeo instead.  It won't make it impossible for people to steal your content, but it doesn't make it as easy as you currently have it.