Sorry, but I don't understand what this (Greek) sentence is trying to convey. Does it mean against in a physical sense, as in the dog is not only adjacent to me, but also leaning into or onto me (I am at least partially supporting its weight)? or is "against" used in a psychological/emotional sense, as in every time I come into the vicinity of this animal, it growls and bares its teeth, displaying fear or hostility?
I agree that this would be a very strange sentence in English. "Against" used this way implies an intentional thwarting of my plans or taking an opposite stand on a principle. This doesn't normally apply to dogs or other animals, even if they are growling or snarling at me. I don't think any of my neighbors would understand me if I uttered "this dog is against me." We might say, "this dog does not like me." in such a situation.
As a native speaker, I think it is a strange sentence in Greek too. It is not grammatically wrong, but Ok, never heard this phrase before about dogs. "Αυτός ο σκύλος δεν με συμπαθεί", "αυτός ο σκύλος δε με χωνεύει", "αυτός ο σκύλος δε με αγαπά", "αυτός ο σκύλος είναι εχθρικός απέναντι μου" and more, are normal to use in Greek in this case. I cannot explain in more, just my Greek language intuition and sense gives me this impression.
I apologise if this is a silly question, but I keep coming back to it. Αυτός here means "this" and the "this" in question is male (ο σκύλος); so far, so good. But sometimes αυτός means "he" as in αυτος τρέχει ... how do I know how to understand the translation? P.S. I have been told that there are no silly questions, but I don't really believe that!
1) The demonstrative pronoun αυτός/αυτή/αυτό (=this) is followed by the definite article ο/η/το (=the) and then by a noun. Note that the demonstrative pronoun+definite article+noun group is in the same case, no mixing and matching! :) Αυτός ο σκύλος, αυτήν την καρέκλα, αυτό το παιδί.
2) The personal pronoun αυτός/αυτή/ αυτό (he/she/it) is followed by a verb. Αυτός τρώει, αυτή δουλεύει, αυτό παίζει. In Greek, because the personal pronoun is clearly implied by the verb ending, you can drop it (Greek is a 'pro-drop' language). Because of that, in this course you will see sentences where the personal pronoun is missing from the Greek sentence and any possible (valid) translation you give in English will be correct. E.g. Μαγειρεύει means (someone) is cooking, therefore you can translate it either as 'he is cooking' or 'she is cooking'. The demonstrative pronoun is never omitted.