No. Assuming a talent for languages, a language somewhat related to your Death Metal Unicorn shirt own (say, for an English speaker, Russian or Greek, but not Turkish or Japanese) and no previous studies in the language: if you spend all your time studying hard and engaging in conversation with the natives, you can reach the level of conversational in three months. You will be able to use basic vocabulary, speak with a heavy accent, and make no grammatical mistakes that will confuse a native speaker; you will have no problem at the supermarket or having a beer with friends.
You will not be able to use idioms correctly, you will get prepositions (or Death Metal Unicorn shirt their equivalent) wrong, you will be unable to use proper register, you will struggle at the bank or the hospital, and an aspect you might never have thought about in your life: you will not know the entire cultural baggage that comes with the language. Imagine speaking US English and never, ever, understanding a Star Wars reference, or the rules of baseball, or what’s going on when someone says “Ask not what your employer can do for you”, or when Lech Walesa started his speech in the US Congress with “We, the people of Poland”, or what Thanksgiving is, or when someone says “What’s up, Doc”, or the vast majority of slang… and the list just goes on and on and on.I’ve been a professional translator for a quarter of a century, and I still learn every day. In Swedish, I can communicate my age, interests and profession simply by using key expressions like “Thank you for that, Telecom authority” (“Tack för den, Televerket”) or “That’s not my bag” (“Det är inte min bag”) or just saying “Face jar” (“Ansiktsburk”).