I’m receiving pension from another country. When I enter the amounts with the average yearly exchange rate, a lower amount appears in the income summary - pension income.

Are you entering the amount in Canadian dollars? If the amount is already in CAD, then you don't need to enter an exchange rate. If you put in an exchange rate, TurboTax will convert the amount using the exchange rate. 

Try to input reciprocal of the exchange rate your using . For example 1.25 instead of 0.8 i.e 1÷0.8

This may give you the results you want.

The alternative is to convert the amount in CAD and input amonut in CAD. Then you dont need to put exchsnge rate. Or input exchnge rate =1.