Cami bahçesinde kuş cıvıltılarını dinlemek çok rahatlatıcı.

In Turkish you express “in the mosque’s courtyard” by first showing possession (the courtyard belongs to the mosque) and then location (in). Morphologically:
• bahçe = garden/courtyard
• bahçe + ‑si = bahçesi (“its courtyard,” 3rd-person possessive)
• bahçesi + ‑nde = bahçesinde (“in its courtyard,” locative case; n is a buffer for ease of pronunciation)
Combine with cami (“mosque”) → cami bahçesinde = “in the mosque courtyard.”

• -lar = plural marker (“chirpings,” more than one chirp)
• -ını = accusative case for a definite object (“to the chirpings” or “the chirpings” as a specific thing you listen to). Because kuş cıvıltıları ends in a vowel, we insert a buffer n before -ı → kuş cıvıltılarını.
Altogether: kuş cıvıltılarını = “the bird chirpings” (plural, definite direct object).

• duymak = “to hear” (passively perceive sound)
• dinlemek = “to listen” (actively pay attention to sound)
Since the sentence implies intentionally enjoying the birds’ chirping, dinlemek (“to listen to”) is the correct choice.

1. rahatlamak = “to relax” (oneself)
2. rahatlatmak = “to make someone relax” (causative)
3. Add the adjectival/agent suffix -ıcı/-ici/-ucu/-ücü → rahatlatıcı
   So rahatlatıcı literally means “something that makes (you) relax,” i.e. “relaxing” or “soothing.”

In Turkish, when an adjective or adjectival noun follows its subject, the copula -dır/-tir is often omitted in everyday speech and writing. The link “is” is understood:
(Kuş cıvıltılarını dinlemek) çok rahatlatıcı.
= “(Listening to the bird chirpings) is very relaxing.”
You can add -dır for formality or emphasis: rahatlatıcıdır.