Can the Venus square be useful to burn karma concerning love and marriage when the moon Is wanning,and how will the energy be programmed .

No, use Munka (destroys karma) or Ansuz (removes obstacles and bindings). You can use Venus to improve your love life, but it is always best to remove negative karma/obstacles before doing a working to gain something.

This thursday is a decent time to do a freeing soul working, waning Moon in Virgo.