"Now it is impossible to go out."
Translation:Ahora es imposible salir.
Salir includes the 'to' in this case as part of the verb "to go out". Some other verbs function this way as well, e.g. buscar is "to search for", the 'for' is already included in the verb buscar. So you would say "Yo busco el libro" to mean that you are searching for the book instead of saying "Yo busco por el libro". It isn't quite the same as the preposition coming before the verb but it's the closest similar example I could think of.
http://www.laspreposiciones.com/verbs-and-prepositions/ this site has a list of verbs that include the preposition and a few examples on how to use them.
I agree that the preposition 'de' isn't necessary here.
The issue here is addressed very clearly by xtempore in another discussion, see:
In this case salir is an intransitive verb, as you cannot put 'it' at the end of the English sentence: it is impossible to go out 'it'. Therefore, no 'de' is needed.
Still, if you use salir as 'leaving' and not 'go out', the verb seems to be transitive: it is impossible to leave 'it'. Nevertheless, I think that salir means more 'to depart' and is not used when leaving 'something', which therefore, also with this meaning, makes it an intransitive verb in English.
I Googled both sentences (es imposible salir and es imposible de salir) in Spanish and both showed a lot of links. Perhaps a native Spanish speaker can shine more light on this.
Why is using 'ya' not correct, since it was listed as one of the options for "now"?
In another sentence it was "empezó a hablar". Although hablar means "to speak", the "a" still was there. Why the "de" is not necessary here?
Verb ''Salir'' means ( to go out ) so there is no need to use ''a'' meaning to :-) I hope that's help:-)
There's no need for a preposition, whether a or de or para, to introduce the verb. Using para is sort of like saying "Now it's impossible in order to go out."