Learn Farsi: لطفاً روی زمین بنشین.

To make a singular command, you add the prefix be- to the present stem of the verb. The present stem for the verb meaning to sit is neshin. Add be- to the front, and you get benshin. You do not add any ending after the stem because it is a command directed at one person. In everyday spoken Farsi, people often shorten this to beshin.

Why does the word lotfan (please) end with an alef and two small diagonal lines?

Those two lines are an Arabic spelling feature called tanvin. When placed over an alef at the end of a word, it creates an an sound. Farsi uses this ending for a few very common adverbs. When you see this symbol at the end of words like lotfan (please), simply pronounce it as an.

Do I need to use the hidden connecting vowel between ru (on) and zamin (ground)?

Yes, you must link them using the ezafe connector. Because ru (on) ends in a vowel sound, the invisible ezafe takes a ye sound to make it easier to say. You will pronounce the phrase as ru-ye zamin. Even though this connecting sound is not written out as a separate letter in the Farsi alphabet, it is required to link the preposition to the noun.

Can zamin refer to the floor inside a house?

Yes! While zamin translates directly to ground or Earth, Iranians frequently use it to refer to the floor inside a room as well, especially when talking about sitting down or placing an object on it.