vampires and demons

Do vampires and demons exist in this world

It depends on how you view "this world". I guess you mean the "material world". No they do not on this world, bu on the non-physical yes they do exist.

It depends. There are people called "energy vampires", which are basically some people who are low on energy and need other people's energy to fill that ( or at least that's how I see it ). But no, there's not such thing as vampires like those in movies and alikes. About demons, that's a different thing; Demons are spiritual entities and are not on this phyisical plane of ours, but they are in planes with a higher vibration, or, the astral plane.

You guys are saying that they are in spirit form and in another dimension why cant we think that they are in our dimension in another form

If they were physical beings science would have be able to prove their existance. Physical=burden of proof. Spirit=up to subjectivity ergo grey zone, neither proven or disproven. Keeping in mind that not everybody takes voice and video recordings to be proof even after the footage has been reviewed and proven to have not been tampered with.