What will happen if an X shape wings mounted on biplane?
Drawing from the hypothetical of "could a starwars X-Wing fly" which is brilliantly answered by James Gull here it is possible to achieve flight in this configuration


  ...It's not a very aerodynamic design. All those intersections at the
  fuselage will create a ton of drag due to interfering aerodynamics.
  The engines and wingtip pylons are not helping in that regard either,
  as they are not well blended in. The wings are essentially a biplane
  configuration, which definitely works. The designer would need to take
  extra care near the fuselage due to the surfaces being so close
  together; their wakes would interfere with each other. Careful tuning
  could help turn this into somewhat of an advantage in slow flight.


The Strop SP-7 was an early proposed design for such an aircraft. But it only 
remained in this configuration for takeoff and slower flight segments, the wings folded into a mono plane configuration for high speed cruise. I cant find any evidence that it ever actually took flight. 

Some aerodynamic "trials" have been done on the "design".

If you are asking about an "X" looking from the top down, it appears that Sikorsky dreamed up something like that and went as far as running tests on the design as well as building some of the major components but the project was ultimately canceled and it never flew.