FRANKFURT—Commerzbank on Friday said its fourth-quarter earnings would be impacted by provisions made at its Polish mBank subsidiary but that it would still post a net profit for the full year. The German lender said mBank had made provisions regarding the foreign currency indexed loan agreements in the amount of 2.006 billion zloty ($504 million), adding that its fourth-quarter results would be impacted by a corresponding amount. The additional sum, which translates to around 436 million euros, brings provisions for Germany’s No. 2 bank to around 600 million euros. The provision is painful for Commerzbank, which is in the midst of a costly restructuring that involves cutting headcount by 10,000 people and closing branches. The issue, which has affected banks operating throughout Poland, stems from more than a decade ago, when mortgage customers took out loans in Swiss francs to take advantage of low Swiss interest rates, only to face …