Pogorszyć się v angličtině:

Corporate results deteriorated because of recession.

deteriorated = decayed, decomposed or became worse over time

Officials believe it contains old coins and newspapers which could have deteriorated over time.

relations between the countries had deteriorated sharply

In 2000 Japan's health care system was the best in the world, but since clinical internship was introduced in 2003 it has clearly deteriorated.

After I returned from Turkey, my Turkish deteriorated.

to worsen the companys' situation