They're basically opposites, if that's what you're asking.
"Get down" is to go downwards. To "get out" is to leave some place, or get something out of some place. To "get off" is to get up from some place or go away, depending on how you use it. To "get on" is to get on top of something or to move along. "Get through" would be to go through something. "Get over" is to get done with something or reach the other side of something. "Get across" is to cross to other side.
That's a lot of "get"s. If I haven't answered your question correctly, please explain more so that I can understand what you're trying to ask.