@Martina407 No, you really shouldn't let anyone "preview" your place. Often they want to do this because they will try to make a private deal with you so they can avoid the Airbnb service fees.
It is also a security issue for hosts- these people could just be thieves wanting a chance to have alook around so they can come back later to rob you or your guests.
Airbnb guests can get all the information they need by looking at your listing photos, reading thoroughly through your listing description and messaging you if they have further questions.