Duplicating values

Duplicating values

I am facing problems regarding refetching or scheduling data import. 
Always is duplicating values for every importation... 

Why does it happen? How to solve it? I have to delete all rows so after I refetch them... boring and unreliable 

Schema:
3 sheets in Xcel in the same worksheet 

1. For goals
2. For store results
3. For salespeople results

Thanks!!
Mauricio.