I read in Blessings From The Battlefield that this Priest was serving in the Korean War, and he and his company found themselves in a village that turned out to be 100% Catholic. He then learned that none of them had been to confession or Mass in years, so he decided to do both. The problem was, though, that he didn’t speak a lick of Korean. However, he still heard their confessions, absolved them of their sins, and then had a Mass afterwards. He said none of them wanted to go as they hadn’t upheld the hour fast, but he told them that it was okay, and they went up to receive the Eucharist. They left afterwards, and a few days later they found out that the entire village was wiped out by the North Koreans. The Priest said he felt confident not just to pray for them, but to pray to them.
Having read this story, I would assume that all of their sins were absolved in the confessional, even though he couldn’t understand what they said. Especially since he had all of them receive the Eucharist.