Unfortunately no suitable babtist online church books (“Raduraksti”) of Ventspils and Riga are available. Maybe this church books (microfilms) can be find at the Mormons (Familysearch), (https://familysearch.org/catalog-search).
A second way to search for Hermanis Redins, his ancestors and descendants would be a comprehensive archive request at the Latvian State Historical Archives (http://www.arhivi.gov.lv/index.php?&110), Department of Thematic and Genealogical Researches. All information on possible requirements, costs, etc. can be found as well on the said website.
However, I have subsequently found: Riga address book1925 «Bernu Draugs». Latv. Red. J. Kronlins un H. Redins. Izd. Latv. Baptistu Draudžu Sab. Redakcija: Maza Nomet?u iel? 14, dz., 13. Izn?k reiz ned?l?.
Translation: "Friend of the child" Latvian Red. J. Kronlins and H. Redin. Ed. Latv. Baptist Sab. Editing: Small Nomet?u Street 14, flat/office #13, Published once a week.
Redin, Hermans, baptistu' m?c?t. (Baptist pastor), Hospit??u iela (Hospital street) 24, d. 1. (flat #1)
Riga address book 1928 Redinš, Hermans, bapt. M?c., Liela Maskavas iela (small Mocsow street) 193-4 (flat #4)
Death notice R?DINS Hermanis, † 08.März 1942 R?gas baptistu draudzes m?c?t?js Zeitung „T?vija” #60, 13.März 1942
Translation Redins Hermanis, † 08. March 1942 Riga Baptist pastor Newspaper "T?vija", #60, 13. March 1942