One of the prejudices is based on the universality of the question. The necessity of asking this question is doubted because we accept the concept of Being as we conceive and comprehend all the beings in the world. There is simply too much 'everydayness' with the concept of Being: we understand the idea of it but merely do not know how to define it, Therefore, some people who consider the discussion of the meaning of Being the "emptiest"; thus the attempt to define Being is worthless. However, Heidegger suggests, although the concept of Being is the most universal, it is not at all the emptiest nor transparent. Instead, because of the fact that Being includes every being but it is not a "category or genus", the question is NOT the clearest.
The other prejudice is that Being is indefinable. Being itself is certainly not a being, neither can it be presented by the beings, and Being is not reducible to beings. Therefore, by the definition of definition, Being can not be defined. Heidegger suggest that, on the other hand, this question of Being has "its foundation in ancient ontology". Besides, the inquiry of the meaning of Being also drives us closer to a better understanding of all beings. This we should look into the question but not get scared away by its "indefinability".
The last prejudice is that when we understand a being, the vague concept of Being is always applied and also correctly, so the meaning of Being is self-explanatory. A certain group hold this assertion against the question of Being. However, Heidegger uses exactly the same notion to defend the very inquiry. He believes that the fact that a concept that has been in practical use but no one understands it makes the question more worth discussing.
The answer to the second question:
A question is 'seeking' of what the questioner has a very vague idea of. Generally, there are three steps for a complete question: asking, investing, and answering. Therefore, all the questions or inquiries about beings consist of that which is asked about [ sein Gefragtes ], that which is interrogated [ ein Befragtes ], and that which is to be found out [ das Erfragte ]. In the question of what Being is, Being is sein Gfragtes, the beings is ein Befragtes, and the meaning of Being is das Erfragte.
The answer to the third question:
Dasein is beings who bring up the question about and of Being while being among the beings that are interrogated; Dasein is den Frager of the very Frage of Being. Dasein is different from the other beings for the fact that Being is an actual issue "in its very Being", which also implies that, contrast to the other beings, Dasein have a relationship toward its own Being. Thus, it's ontological instead of being ontic because Dasein is. Before the discussion in the class, it had appeared to me that only superior beings such as a portion of humans can be counted as Dasein. However, Dasein is beyond any the notion of beings. So it Jerry cannot be Dasein, Alfred cannot be Dasein, and a chair cannot be Dasein, but the Being of them that raises the question and interrogates themselves is Dasein. The first of Dasein's priorities is that Dasein understands itself existentielly and can choose what to be of itself. Secondly, Dasein is able to understand the Being as t in itself and in other beings, which is ontical as the first priority is. The third one, which Heidegger calls 'ontico-ontological', is that Dasein make ontologies possible because Dasein as the Frager that is being Befragte provides an opportunity for Being to be revealed.