When one country imports something from other, how the bank makes payment to other country? Did they send notes after online foreign exchange or what?

Hi 

for import and export method u should communicate to your bank By LC ( Letter of Credit ) 

so your bank will charge you about 2% of commercial invoice value , so your bank will insure for the exporter or Supplier to grantee his money once the goods arrived at yours place .

Majid, As salaam alaykum 

A country can acquire foreign currency in the international currency exchange market, as long as it can pay for the currency required, for example with its own currency. Alternatively, it can negotiate the payment in its own currency, if seller is willing to take the currency.  Payment terms can vary, thus the exchange of currency can be within an agreed upon time period.

Hope this helps?