Well this is Interesting, But I fear there is no special resources like apps, websites, tutorials to learn Havyaka. You may find some books somewhere.I think the best way is to speak with someone who knows.
It uses similar verbs and words as mainstream Kannada. However, it has more in common with Halegannada. This might be the reason why even native Kannadigas find it difficult to comprehend it for the first time.
It is spoken in the regions of Mangalore, Sagar, sirsi, Honnavara, etc.
Havigannada was partly used in Films like Bettada jeeva, nammora mandara hoove, Naayi neralu.