Why is "je marche a la porte' wrong? Does not 'vers' mean 'toward'?
"vers" means "toward" (in the direction of).
"à la porte" does not work with verb marcher but you can say : "je frappe à la porte" (I knock on the door).
I did some restricted searches on google (with double quotes). "Je march à la porte" got 6000+ hits, whereas "je march ver la porte got 1000+ hits. That suggests that the former is correct.
With the right spelling, indeed "je marche vers la porte" is correct.
Thanks, I wander if it is possible to figure out which verb goes with what in French! Rather peculiar logic, if there is one at all, it seems!
It is the same for French people when they learn English...
That is at least, some comfort, though not much.