In 1910 relations wouldn't have been particularly difficult; Germany was no more anti-semetic than other European countries at the time. A lot of the sections on the map labled "German" might have actually included many German Jews that had migrated in the 1840s-60s, and identified more as German than Jewish. The actual "Jewish" section on the map, the old Third Ward, was mostly more recently-arrived eastern European Jews.

By the 1930s though, there were tensions between the Jews and Germans. By that point, many Germans had moved to either the far western edge of the city, or to Irvington, while the Jews had begun to move into Clinton Hill. The pro-Nazi German-American Bund operated out of a headquarters on Springfield Avenue and battled in the streets with Jewish Newarkers. Newark Jews organized a self-protection group, known as the Minutemen, with the help of Jewish mobster Abner Zwillman, and basically crushed the Germans' power.

Check out Warren Grover's Nazis in Newark to learn more,

Most of those neighborhoods were probably folks who knew of each other - lots of migrants came from Germany in the 1840s-50s, I believe.