Exchange Rate Difference- Purchase Invoice

I have Certain Doubts regarding Exchange rate difference. See we purchase items from foreign countries on 60 days credit basis. So at the time of Processing Purchase Invoice we set a default exchange rate (Eg. For USD to OMR =0.386 ), And we make payments after 60 days so at that time of making the payment the exchange rate may be different ( Say USD to OMR = 0.380). So gain in exchange rate . So in this case how ERP NEXT functions… Since their is no Supplier statement available in Foreign Currency How we make the payment.

Make payment entry and enter the difference in the deductions /loss section

Thank You. one More thing . Can you tell me , how to maintain two warehouses. one for retail and one for applications

You can create multiple warehouses and select appropriate warehouse while making stock transactions (Purchase Receipt, Delivery Note, Stock Entry etc.). Documentation here.