Dobro sam, hvala means “I’m fine, thank you” – the answer to kako si? and kako ste?.
The person opposite you holds a tin in one hand with bread sticking out of it and a few seeds on top: tin, bread and seeds give you dobro sam. In the other hand there is a whale that keeps laughing – that is the hvala from video 5, with its hissing opening sound.
Practise these four sentences together and you already have a complete little exchange in Croatian.