Well, if I'm on one side of the bridge and you're on the other, the bridge is between us and you're behind the bridge, but it sounds more normal to me in English to say "over the bridge". Of course we could both be in the river on opposite sides of the bridge, when I would say "behind the bridge". I'd say that should be accepted too.
The less context provided, the more translations should be accepted. With no context, "behind the bridge", "across the bridge", "on the other side of the bridge", "beyond the bridge", "over bridge" and "past the bridge" could probably all be used here. It just depends on the situation.
After reading these comments, I feel even more confused. I would love for a native speaker of Russian (with a high level of english, with no double speak or trying to be too smart by half) to explain exactly "how" a russian speaker would say, "I am going over the bridge" also "he/she/it/they is/are on the other side of the bridge". If there IS some wonderful person who feels like taking up this challenge, I would be very appreciative )))
Not quite; "over the bridge" is also used to mean "on the other side of the bridge", possibly because "over" is also used like по sometimes, so "an overland journey" is made on land. See also "override", "we went over this material already".
Of course, if we said "the drone is over the bridge" we would mean над.
Sorry, I meant that as a helpful analogy, not to lead you astray. Indeed "по этому мосту" would mean "over this bridge", but only for motion. For location, you should use за.
My point (obviously poorly presented) was that "over" has multiple context-dependent meanings.