This is the 53rd most frequent Czech word.
velmi
"Velmi" means "very" in English.
Here, 'velmi' is used to intensify the adjective 'šťastný' (happy).
Jsem velmi šťastný.
I am very happy.
In this sentence, 'velmi' modifies the adjective 'zajímavý' (interesting) to emphasize a high degree of interest.
Tento film je velmi zajímavý.
This movie is very interesting.
'Velmi' here enhances the verb phrase 'se mi líbí' (I like) to express a strong appreciation for something.