There is way more advanced help on this forum but let me stab at it. No you don’t need to be online as long as what you want to watch, see, or listen to is attached to your raspberry pi. Anything for your home network or off the internet will need access to your router. Are you using hdmi? Try going to the audio settings under system/settings/system/ audio output. Set the audio output device from there. Are you playing audio through your tv or computer speakers or do you have an audio video receiver. I use an audio video receiver so I enable passthrough to let the receiver do all the work. If you do not have a receiver then make sure passthrough is not enabled. Obviously try a reboot. If you haven’t already, many things on the pi will begin to work after a reboot if anything was changed. The Pi is supposed to handle 1080p playback. There are 2 video licenses you may need to purchase for about 3-4 u.s. dollars from the pi store for best possible playback. As far as the dvd player, I haven’t tried it myself but first you need a player that has its own power source or a separately powered usb hub. The pi isn’t set up to supply a lot of power to devices. Also from my own linux experience, dvd playback can be a pain because of licensing and encryption. I got it to work once in ubuntu but I forget how. You should be able to access files that you put onto a dvd though. To watch your store bought dvd movies you will need some tweeking or a network work around because your software isn’t set up to read store bought encrypted movies. It is possible, I just don’t know the answer.