Translation:Let's eat apples before going there.
Your two comments about "önce" are greatly concise and useful: may I suggest adding them to the notes for this lesson?
I also want to take this opportunity to thank you and other contributors for the very helpful comments in the Turkish course on Duolingo. In order to reduce the clutter, I don't always thank people for their answers (although I "like" the comments or give lingots). Not all courses are as good on this regard.
That isn't the translation of this sentence. If a direct object is singular in Turkish, you have the option of having it be singular general or plural general in English.
To say "to eat apple" is only right for some English speakers and it means "to eat things containing or flavored like apples." That would be translated differently in Turkish. ("I eat apple" sounds really bad to me, but it is more ok for British people :D)