I've tried to look here:
But it's not clear to me. Also I don't understand why über-queren should literally translate as over crossing.
Can you help me?
Überqueren requires that you cross something that's physically located beneath you. Take
Die Straße überqueren (crossing the street)
Im Flugzeug den Kanal überqueren (crossing the Channel by plane)
Queren describes a traversal where the movement is roughly perpendicular to a (often implicitly) contextually defined preferred orientation of what is being crossed.
Die Nordwand queren [alpinism] (traversing the north face).
- The contextual orientation is vertical while the mountaineer climbs from one side of the face to the other, though often not strictly keeping his altitude.
Ein querender Fußgänger (a pedestrian crossing our path).
- The contextual orientation is your own bearing.
Both verbs indeed mean "to cross" (i.e. a river). The "über" can be used to indicate two things in the sentence "Wir überquerten den Fluss":
So without an extra indication on the means how you got over the river, the two terms can be used exchangeably, except that you cannot say "überqueren" if you meant to go under it.
queren may be used interchangeably with
überqueren, the word
überqueren has a stronger connotation with acts of motion while
queren is used more in a geometrical sense.
If you google "überquert den Fluss" (Fluss = river) you will mostly see search hits concerning entities (humans, animals, cars) actively moving from one side of the river to another.
On the contrary, if you google "quert den Fluss", you will find search hits that rather discuss geographical situations in the sense that a bridge or street is crossing the river.
Die Brücke überquert den Fluss
...is formally correct, as it physically crosses the river from above (~
über), but it also arouses the association that the bridge is an enitity that is actually capable of movement and is currently engaged in the activity of traversing the river.
Die Brücke quert den Fluss
Would remove the connotation mentioned above and make it clearer that "the bridge crosses the river" in a geometrical sense.