Learn Farsi: مکانیک ماشین‌تحریر قدیمی را به طور کامل تعمیر می‌کند. - The mechanic repairs the old typewriter completely.

It uses the target structure for this lesson: the fixed phrase be tor-e (literally "in the manner of") followed by the adjective kâmel (complete). This translates to "completely" and is one of the most common, productive ways to turn adjectives into adverbs of manner in Farsi, working very much like the "-ly" suffix in English.

Could we use be surat-e instead of be tor-e here?

Yes, you could say be surat-e kâmel. Both be tor-e and be surat-e (in the form of) are interchangeable when creating these adverbial phrases of manner, and both sound completely natural in this context.

Why is be tor-e kâmel placed right where it is in the sentence?

Adverbs of manner generally sit immediately before the verb. Because ta'mir mikonad (repairs) is a compound verb, the adverbial phrase is placed right before its non-verbal part (ta'mir), separating the direct object phrase from the verb.

Can I put the adverbial phrase inside the compound verb, like ta'mir be tor-e kâmel mikonad?

No, you should avoid breaking up the compound verb with an adverbial phrase. While native speakers sometimes slip tiny words (like pronouns) between the halves of a compound verb in very casual speech, multi-word adverbial phrases like be tor-e kâmel strongly belong before the entire compound verb.