I will have been studying Italian for three years. Here 'will have been studying' is an example of:

Noun Phrase

Verb Phrase

Adjective Phrase

Prepositional Phrase

Explanation

A verb phrase consists of a main verb and its auxiliaries.
In this sentence, will have been studying is a combination of auxiliary verbs (will have been) and the main verb (studying), forming a future perfect continuous tense.