Yes, that's already accepted, though I think Η πίστη σ' αυτήν τη θρησκεία is better -- with final nu on αυτήν since it comes before a tau (and σε is often abbreviated to σ' before a vowel).
If the word after "αυτή" starts with α,ε,ι,υ,η,ο,ω you add the ν in the end
That's what makes it complicated! I just worked out the following to see if it can help me:
Use αυτήν when followed by a vowel or voiceless stop consonants π,τ,κ, or some combination of these with a nasal (n,m) or s/z: π, μπ, ψ; (labial) τ, ντ, τσ,τζ; (dental) κ, γκ, ξ; (velar)
Use αυτή with: ρ, λ, (semi vowels) μ, ν, (nasals) And (voiceless/voiced fricatives (with a vibrating, buzzing sound)) θ, δ, and σ, ζ, (dentals) φ, β, (labials) χ, γ, (velars)
"Η πίστη σ'αυτή τη θρησκεία." Is what a Greek would say.
It should have been accepted.
"Η πίστη σ'αυτή τη θρησκεία." is already one of the accepted translations. If it wasn't accepted there might have been another error. Please send screenshots for these issues.
Faith in someone/thing means trust. Religions have a set of beliefs which are combined in the faith. You would talk about the Christian faith, which is different from the set of beliefs that is the Muslim ... faith. So it would be the faith (set of beliefs) of a religion.