Complex sentence: Even during his stay in Kodagu district during the years (1853--1858) he spent lot of his time on proselytisation and he also published a German book titled "Das Kurgland" which mainly deals with his activities related to Christianity.
Split into simpler sentences: Even during his stay in Kodagu district during the years (1853--1858) he spent much of his time on proselytisation. Je also published a German book titled "Das Kurgland" which mainly deals with his activities related to Christianity.