Learn Arabic (Modern Standard): كم خطوة مشيت؟

In Arabic, the question word كم (kam), meaning "how many", is always followed by a singular noun. So instead of saying "how many steps", you literally say "how many step".

Are there any special pronunciation rules for the word خطوة in this sentence?

Yes. In formal Modern Standard Arabic, the singular noun that comes right after كم (kam) must take an "-an" sound at the end (the accusative case). So خطوة is pronounced "khuTwatan". However, if you are just speaking casually, people often drop that ending and just say "khuTwah".

The word مشيت means "you walked", but does it refer to a man or a woman?

Without the short vowel marks written above and below the letters, مشيت is spelled exactly the same for both! You have to know from context. If you are asking a man, you pronounce it mashayta. If you are asking a woman, you pronounce it mashayti.

Why is there a ي (yaa) in the middle of the verb مشيت?

The dictionary root for the verb "to walk" ends in the letter ي (yaa). When you conjugate this verb in the past tense for "you", you attach the letter ت to the end. The original ي stays right where it is, creating an "ay" sound before the ending: mashay-ta or mashay-ti.