Hi Alok,
If you Import Purchase Supplier is in EUR Currency then you have to make that Supplier Currency in EUR or if you are dealing in different Currency then you have to make this Supplier as All Currency.
If you will Make this Supplier as EUR Currency then you will be able to do transactions for this Supplier in EUR.
If you will make this Supplier as All Currency then also you can do transaction in EUR buy you have to change Currency to EUR while Creating Document.
From below path you can make Default Currency to EUR or All Currency for this Supplier.
Business Partner >>> Business Partner Master Data >>> Currency Field.
Hope this helps 
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Regards::::
Atul Chakraborty