please interpret my dream ...!?

A basement floor is something you stand on, or you build on, like your past. We all have a past and share some of the events which have happened to us in the past. By digging to find another floor, under the basement floor, it shows that there is more to your Father's past then what he is telling you. You would be wise to press him on the issue, and ask him for details of his Life before he had you. I would not concern him with the dream symbolism, but just say you were wondering about his Life and what he did as a young man, etc. Hope you get more information and don't have to "dig too hard" to find out the answers you are looking for. Best of luck to you Syed.