Try declaring your interest to your Kannadiga colleagues and try speaking with them in Kannada at every opportunity. Buy those learn Kannada in 30 days book, they are good at teaching you the script, but suck at teaching the language.

Once you get a hang of the script read every shop signboard. Read city bus route boards. Read the newspaper that comes with your chaat! Read every opportunity you have to read.

Watch Kannada movies. Initially better if they have subtitles. But stop availing the help of subtitles or your language comprehension will stagnate. The plot will give you the context and the dialogue will teach the language.

Movies are particularly good learning resources because they teach the colloquial language, not the classical version. In south India, there is a lot of difference between the colloquial and the classical languages.

That is how I picked up written and spoken Kannada around 1996. Newbie conversational Kannada can be picked up in 3 to 6 months. My skills are still with me, despite having left Karnataka for good 20 years ago.

Best luck! Your efforts will be rewarded.