I'm not a teacher, but I have found some bits you could find useful.
From 'over' vs 'above'
You ask for a difference in meaning between over and above. Over suggests that there is some connection at the sides assuming an arch shape/form(but not always) as in the bridge over the river. Above suggests higher than something as in the moon above the skyline. These are very simple explanations and more than likely there are a dozen exceptions. You could in fact be standing on the bridge over the river from where you could see the moon above the city lights in the distance.
From March 2007: Grammar Trap: More and Less vs. Above, Over, Higher, Below, Under, and Lower
Let’s say record numbers of people will watch this year’s NCAA Men’s Basketball Championship.
Can I write, “Over 100 million people will watch the game on TV”?
I can, but I’d be wrong.
I really should write, “More than 100 million people will watch the game on TV.”
That’s because you should only use “over,” “under,” “above,” “below,” “higher,” and “lower” to describe physical relationships in space. For just about everything else — especially numbers — use “more” or “less.”
The bear climbed over the mountain. The eggs are under the toast. The detergent is in the cabinet above the washing machine. The creepy basement is below the trapdoor. The ceilings here are higher than in our old place. The river is lower than it was last week. But there are more than 100 people here and less than half of them know what they are doing.
There are some exceptions. For example, you can use the “space words” metaphorically. For example, “The CEO is above everyone and she often holds her authority over us.” Or, “Grammar Trap standards seem much lower these days.”
It’s also acceptable to use “above,” “below,” and the rest when referring to temperature. We say it is “below zero” not “less than zero.” Most likely, this harks back to the old days of reading the temperature by the mercury level in thermometers. Still, there are less than 3 inches of snow, not under 3 inches.
I can’t say I’ve helped more than 100 million people with this advice, but I hope I hear more than a little positive feedback.
Besides, you can use "over" in phrases like:
"over there"; "over" meaning here that you can actually see where they are pointing at.
"over and over"; meaning again and again.
I hope it helps.