موعظه کردن <-- Advise (Verb) --> نصیحت کردن
Pronunciation /məʊ'ɛzɛ/
وعظ <-- Advice (Noun) --> نصیحت
Pronunciation /væ'z/
بال <-- Wing
Pronunciation /bɑːl/
پر <-- Feather
Pronunciation /Pær/
We say 'پر و بال' or 'بال و پر' together, when we want to say something is able to fly.
It's an idiomatic expression.
و الا <-- Otherwise --> در غیر اینصورت
Pronunciation (Two words together) /væ/ /ɛllɑː/
خراب شدن <-- Destroy --> ویران شدن
Pronunciation /khærɑːb/
در اثنای <-- During --> در میان / در خلال
Pronunciation /æsnɑː/ Also /æθnɑː/ (It depends on the accent)
You can say /æθnɑː/. But we don't pronounce the /θ/ sound in Persian.
The /θ/ sound is an Arabic sound. /ث/ --> /θ/
It exists in our alphabet. In fact, we prefer to use the /s/ sound instead of /θ/ sound.
But if you can pronounce the /θ/ sound, it's better to say it.
In other words:
The /θ/ sound isn't common in Persian. But it's correct and acceptable.
In the end, the sentence you've given is a VERY formal sentence.
We don't use this kind of sentence in spoken Persian. It's not informal.