"Are you alone?"
https://www.rocketlanguages.com/italian/grammar/italian-adjectives this information should explain and should be in adjectrves lessons, while i guess it's not. the sentence itself shouldn't be in adverbs lesson.
Here's a link to someone who asked the difference between "sei" and "stai". The top answer is from an Italian person who lives in Italy. You may find it helpful.
From what I've read, it seems that "da solo" means "on your own", whereas "solo" is more in the context of "lonely".