Answer:
Inconclusive
Step-by-step explanation:
The question lacks details about the value of the stocks of the German company.
Assuming the stock initial value at Peter's purchase is £100, after which there was a 20% decline (£100-20%) over the last year, then the euro appreciated over the year by 10%; meaning (£80+10% = £90).
If Peter sold the stock today his returns is -10% because his returns is 10% lesser than the initial stock value.