In the responsa Zioni, vol. 1, section 70, a responsum to him from the year 5614 was printed (where he is called “the Av Beit Din of the congregation of Preil”), and apparently he is also mentioned there in vol. 2, section 15 (“regarding the matter that the rabbi of the congregation of Preil posed a question on a ruling”), and at the end of section 44: “and I received a letter from my friend the rabbi our master R. Naftali Hertz, may he live, of Preil.” He is also mentioned in Toldot Yeshivat HaYehudim BeCourland, p. 156, in a note. Shem HaGedolim HaShlishi (manuscript), where it also says that his son R. Nissan Yaakov was also rabbi here and passed away on Rosh Chodesh Kislev 5644 at age 54, and his livelihood came from running a shop. But I am uncertain whether he indeed served here as rabbi as well, and I have not seen this mentioned in other sources.