Learn Farsi: پدر من الان خسته‌ست، اما در پارک پیاده‌روی می‌کنه. - My father is tired right now, but he is taking a walk in the park.

This is a perfect example of colloquial spoken Farsi. In formal or written Farsi, the third-person singular (he/she/it) ending for verbs is -ad, which would make this verb می‌کند (mi-konad). However, in everyday Tehrani speech, that -ad ending changes to an -e sound, turning it into می‌کنه (mi-kone).

Why is the word for "is" written as ست attached to the word "tired" (خسته‌ست)?

In spoken Farsi, the verb است (ast - "is") often merges with the word right before it. Because خسته (khaste) ends in a vowel sound (an "e"), the "a" sound in است drops out completely. It leaves just ست (-st) attached to the end, so it is pronounced khaste-st instead of khaste ast.

How exactly does پیاده‌روی می‌کنه translate to "taking a walk"?

پیاده‌روی (piyāde-ravi) is a noun that means "walking" or "a stroll." It is built from پیاده (piyāde), meaning "on foot," and روی (ravi), meaning "going." Because Farsi loves compound verbs, it pairs this noun with the "to do" verb, کردن (kardan). So, literally, "taking a walk" translates to "doing foot-going."

Why does در پارک (in the park) come before the words for "taking a walk"?

Farsi is a Subject-Object-Verb language, meaning verbs like usually go at the very end of the sentence or clause. Because acts as a single compound verb unit, its two pieces stay tightly glued together at the end. Any extra details, like the location (), naturally get placed right before that verb block.