a verb is an action
yes
The word smug is an adjective. Smug means pleased with oneself.
The word believe is a verb (believe, believes, believing, believed). Noun forms are believer, believability, belief, and the gerund believing. Adjective forms are believable and believed.
It seems like there might be a typo in your question. If you meant to ask if "so" is a verb, the answer is no; "so" is typically used as an adverb or conjunction to indicate degree or consequence. If you meant something else, please clarify!
L'amour devrait durer pour toujours! is a literal French equivalent of the Italian phrase L'amore dovrebbe durare per sempre! The respective pronunciations of the phrases -- which translate into English as "Love should last forever!" -- will be "la-moor duh-vreh dyoo-rey poor too-zhoor" in French and "la-MO-rey do-VREB-bey doo-RA-rey per SEM-prey" in Italian.
The word 'shouted' is the past participle, past tense of the verb to shout. The past participle of the verb is also an adjective. Examples: Verb: Someone shouted, 'There it is!' Adjective: The shouted instructions were hard to understand.