For people who go traveling and aren’t fluent in the local tongue, it’s obviously helpful to at least be able to use the verb “to speak,” as in “I don’t speak [your language].” or “Does anybody here speak English?” I’m here to help you out, in Persian, in Arabic here, and in Turkish here.
The verb “to speak” is صُحبَت کَردَن (ṣuḥbat kardan). There are other verbs that have similar meanings (to talk, to converse, etc.), but for the physical act of speaking this is what we’re going with.
The two key sentences are “I don’t speak Persian” and “Do you speak English?” so that’s what we’ll look at. In the first case you’ll see first-person, singular, negated form of the present-tense verb, and in the second you’ll see the second-person, plural form since that is more formal than the singular (and presumably if you’re asking someone if they speak English, you’re on formal/unfamiliar terms with them).
“I don’t speak (the) Persian (language)” is مَن) (زَبانِ) فارسی صُحبَت نمی کُنَم) (man zabān-i fārsī ṣuḥbat nimī kunam, “man-za-baan-e-faar-see-soh-bat-neh-mee-ko-nam”). مَن is the first person singular pronoun, and may be omitted since the verb conveys the same information (first person, singular). زَبان means “language” and is also optional—as in English we can just say “Persian” instead of “the Persian language.” Adding the “ni” particle in front of the progressive marker (mī) negates the verb.
If you prefer to say “I don’t know Persian,” which isn’t as polished as “I don’t speak Persian” but still worth knowing, you can say مَن) (زَبانِ) فارسی (را) نمی دانَم) (man zabān-i fārsī rā nimī dānam, “man-za-baan-e-faar-see-raa-neh-mee-daa-nam”). را marks the word before it as the direct object of the verb, but you can get away without it in this case. The verb for “to know” is دانِستَن (dānistan, “daa-ne-stan”).
“Do you speak English?” is going to be آیا شُما زَبانِ انگیسی صُحبَت می کُنیم؟ (āyā shumā zabān-i inglīsī ṣuḥbat mī kunīm?, “aa-yaa-sho-maa-za-baan-e-in-glee-see-soh-bat-mee-ko-neem”). آیا is untranslated and just introduces a yes/no question, and is quite often left out (but be sure your tone of voice conveys that you are asking a question if you do leave it out). شُما is the second-person, plural pronoun and can be omitted here since the verb conveys the second-person plural information. Again, زَبان can be omitted (and probably should be in conversation).