Please forgive me for using English only. I am researching my mother-in-law's relatives. Neither my husband nor I speak German or Serbian, so I must write my query in English.

I am looking for information about the following people. They were "German Slavs" (also known as Danube Schwabians):

a) Franc Berwanger (d. 1946) married Anfang-Franciska (last name unknown - 1879 to 1908). They had two boys: Franc (or Franz; b. 1901) and Peter Berwanger (b. 1906).

b) Franc (b. 1901) married Anna Weifert (b. 1904). She was the daughter of Anton Weifert (b. 1874; d. 1926) and Magdelena Engler (b. 1880; d. 1946). Anna had two brothers (Joseph: 1898 to 1970 ; and Anton: 1902 - 1945). 

I know Franc Berwanger (born 1901) came from Vrsac (Banat region) according to immigration papers (he, his wife, and two of their children moved to Canada in 1929). I'm assuming his wife, Anna, also came from that region. I am told that her family had vineyards and the wine was sold locally, I guess. I think Franc and Anna also had vineyards once they married.

With this research, I am hoping to find out a few things: 

I would like to find birth certificates, marriage certificates, and cemetery records. Perhaps I will also find out names of previous generations.

Finding relatives would be a bonus. 

Thank you all for your help.