I really don't understand how does the calculations work
I have got 6.5 in all sections except for listening I got 6
What is my score and what will be my CLB level then?
That will be a CLB 7. If you had 6.5 in listening also it would have been CLB 8. You can verify it from the charts here http://www.cic.gc.ca/english/resources/tools/language/charts.asp