Hm, where can I report a mistake? The word "to" (να) is not a preposition here; it is part of the infinitive form of the verb. A preposition must usually be followed by a noun (the object of the preposition) or an implied noun, not a verb. "Να" plus the verb is usually the way that the infinitive is formed in Greek, just as "to" followed by the verb is the way that the infinitive is formed in English. I am by no means an expert in Greek, so would like confirmation of this. Thanks.
In English, a single word can be used in a variety of ways. For example, the word "inside" can be used as a preposition (She colors inside the lines.) or as an adverb (I'm going inside now.) The word cannot be classified as a preposition or as an adverb until it is used in a sentence. The word "to" is another word that can be used as a preposition (I'm going to the store) or as something else - most often as part of the infinitive form of a verb (I'm going to run tomorrow.) . The word "to" is not a preposition in this sentence; it is part of the infinitive. My understanding is that in Greek, the word "να" is not a preposition (it does not come at the beginning of a prepositional phrase!); it is part of the infinitive, just as "to" is part of the infinitive in English.
There's no infinitive form in Modern Greek as such so in place of the to+verb structure in English we use the first person singular in Greek verbs. With that in mind, here's how your phrase reads:
Το αγόρι θέλει να τρώω τυρί. = The boy wants me to eat cheese. ('The boy wants that I eat cheese')