Final "ν"

I would advise you to keep the final "ν", as it isn't incorrect to use it when it isn't needed. However, it sounds wrong if it isn't used in certain cases.
The final "ν" applies to the definite article "την" and the negative adverbs "δεν" and "μην".

The final "v" is maintained
1. when the following word starts with  a vowel (α, ε, η, ι, ο, υ, ω)
i.e. την Ακρόπολη

2. when the following word starts with the palatal consonants κ, π, τ, and the consonant clusters μπ, ντ, γκ, τσ, τζ
i.e. την κοπέλα, την μπάλα.

 3. when the following word starts with the double letters ξ, ψ
i.e. δεν ξέρω, μην ψάχνεις

The final "v" is omitted

1. when the following word starts with the consonants β, γ, δ, ζ, θ, λ, μ, ν, ρ, σ, φ, χ
i.e. τη γάτα,  δε σκέφτομαι, μη φτιάχνεις
Note 1: The final "ν" is maintained in the form of the personal pronouns (emphatic/ strong form) "αυτόν", "αυτήν" and the personal pronouns (weak form) "τον", "την".
i.e. αυτόν τον σκύλο, αυτήν την τσάντα, τον συνάντησα, την βρήκα.
Note 2: If the masculine form of the pronouns is the object of the sentence then you should keep the final "ν".
i.e. Δεν είδα κανέναν.
Αγόρασα τον άλλον.
Ποιον πήρες τελικά;
Όποιον και να ρωτήσεις .....