"Jesteś za granicą?"
Translation:Are you abroad?
Why here za granicą is with an ą, and in the other one, where it says "Jadę za granicę" it is with an ę?
Different cases. Right now you are 'behind the border', and 'za' = 'behind' takes Instrumental.
You can go 'to behind the border', so to say. As this involves movement, this 'za' takes Accusative instead.
so "Jestem za granicą" and "Jadę za granicę"...? Because the first doesn't imply movement but the second does?
Can this also mean, in a more litteral sense, 'Are you behind the border?' ?
Yes, although that would be rather unusual. Anyway, added now.
I translated : < are you behind the border > it was not accepted. I had to put < frontier > so it is not accepted yet.
"Are you behind the border?" is accepted, it should have worked. "frontier" is not. Well, it is now - added.