Illusionist Denis Behr talked to The Post's Cindy Adams about his legendary career performing card tricks. Brigitte Stelzer for NY Post Trip to B’klyn is in the cards Magician Denis Behr. German. In NYC now. Pay attention. Word is he’s the world’s best in card tricks . His English, perfect. Black shirt, black pants, perfect. Imperfect is his small “theater.”  It’s behind a secret partition in a smaller than my john Brooklyn store selling shticks and tricks. He’s behind a simple table. The tiny clustered room has no video, no cameras, no special effects, no clever lights, no soft cushiony seats. Nothing. Just him. Audience of maybe 20,  it’s 69 Atlantic run by Hal Schulman , who charges $200. He’s there through Saturday. Why was I there? My friend, lawyer Stuart Slotnick’s dad Barry Slotnick is the famous lawyer. Between lawsuits, Stuart loves card tricks. Behr: “I began age 7 after I was given a set of magic tricks. It fascinated me. I began to learn the truths behind them.…