The correct answers are Maybe we should order some pizza for the guests. and The pizza delivery guy may be lost in our neighborhood.

Maybe (one word) is an adverb that means "perhaps" or "possibly." It usually goes at the beginning or end of a sentence.

May be (two words) is a verb phrase showing possibility. It acts as the action or state of being in the sentence (e.g., he may be lost, she may be late).