What skill progress level would constitute fluency in a language?
While learning the vocabulary, grammar, pronunciation, and listening comprehension skills on this site are a great start, fluency will not be gained by lessons alone. For fluency you really need to take the skills you learn from here and get out there. Go live in a foreign country for several months or years. Use your language skills to express yourself, to ask for help, and to communicate. You'll develop coping strategies to communicate even when you don't know the word for something or can't produce the proper grammar. You'll need to speak in your new language even when you're tired or cranky or sick. It's that daily usage that really polishes your knowledge into fluency. But, until then, look around your area. Many cities have small meetup groups of folks who want to practice a particular language. Casual immersion settings like that are great for taking your textbook skills and pushing them towards communication.