Learn Farsi: برای اینکه ماشین‌تحریر خراب نشود، از آن به طور صحیح استفاده کن. - So that the typewriter does not break, use it correctly.

In Farsi, you can turn an adjective into an adverb of manner (similar to adding "-ly" in English) by placing be tor-e or be surat-e before it. Here, the adjective sahih (correct) follows be tor-e (in the manner of) to create the adverbial phrase be tor-e sahih (correctly).

Could I use be surat-e sahih instead of be tor-e sahih here?

Yes, they are almost entirely interchangeable for this purpose. Both be tor-e and be surat-e are standard structures used to form adverbs from adjectives. While be tor-e is sometimes preferred for more abstract concepts, both are perfectly natural in this context and mean "correctly".

Why is there an az before ân (it)?

The verb "to use" in Farsi is the compound verb estefâde kardan. This verb specifically requires the preposition az (from). So literally, Farsi speakers say "make use from it" (az ân estefâde kon), rather than attaching a direct object.

Why is the verb našavad (does not break) in the subjunctive mood?

The clause begins with barâ-ye in-ke (so that / in order to), which establishes an intended outcome or purpose. Because this outcome is a goal rather than an already realized fact, the verb that follows must be in the subjunctive. Here, it is the negative subjunctive of šodan (to become).