Learn Farsi: شاید مدیر این بدهی مشکوک را کاملاً فراموش کرده باشد. - The manager might have completely forgotten this suspicious debt.

Because the word shâyad (perhaps/might) creates doubt about an action that happened in the past, we use the Present Perfect Subjunctive. You form this by taking the past participle of the verb farâmosh kardan (to forget), which is farâmosh karde, and adding the subjunctive copula (the "to be" verb). Since the manager is third-person singular, we use bâshad. Together, shâyad ... farâmosh karde bâshad means "might have forgotten".

Why does the object marker râ come after the adjective mashkuk instead of the noun bedehi?

The word râ marks a specific direct object, but it always attaches to the end of the entire noun phrase, not just the main noun. The whole object phrase here is in bedehi-ye mashkuk (this suspicious debt), so râ is placed at the very end of that phrase.

Is there a hidden ezâfe (linking sound) between the words for "debt" and "suspicious"?

Yes, there is an ezâfe linking bedehi (debt) to its adjective mashkuk (suspicious). Because bedehi ends in a vowel (the "ee" sound), the ezâfe is pronounced as -ye to make bedehi-ye mashkuk. It is usually not written in the Farsi alphabet, but you must pronounce it to connect the noun and adjective.

Why does the word kâmelan look a bit different from normal Farsi words?