Some language learning tools such as textbook, spaced repetition software or traditional lessons are popular and rightly so: they are effective.
Anki will help you gain vocabulary, and so will reading books (plus the more you read, the more competent at reading you will be), you may watch movies or listen to podcast to improve your hearing comprehension or sign in langcorrect.com to get better at writing in your target language.
As language acquisition is a long term process, those methods needs to be fun in order to be effective, lest the learner drop the habit out of boredom (and yes, some people do think Anki is kind of funny).
Things gets a bit tricky when it comes to finding a fun way to train conversation skills. Aside from hiring a personal tutor on italki , or finding a regular language exchange partner, there are not a lot of options.
I was looking to use role playing game in this context for any of my target languages before deciding to organize some sessions in French, for the benefit of people learning it. Turns out the sessions are fun to play and help not only with listening comprehension but also with sentence generation.
Obviously, sometimes, communication is done in an other language that the one being studied. Clarifications, questions (“Hey, how can I say ‘you should not believe everything this guy is saying’ in French ?”) or game rules mechanisms descriptions are often being spoken, for the sake of clarity, in something more easy to understand.
There are several factors that makes role-playing game a good exercise for language acquisition:
I heard lots of people interested in language study telling that the best complexity level one should expose itself to in order to progress in a language is slightly above one’s comfort zone, so that understanding is challenging enough while not being completely impossible.
Even when there are a lots of things a player do not understand in the description he hears from the game master, he can manage to make sense out of it using extra verbal clues such as the information available on the battle-maps, the reactions of the other players, and the context in general.
Most of the in game interactions are stereotypical and follow the same pattern: the players look for information, ask questions to a NPC, or state the action they want to perform (“I hit this monster”, “I open the door”, “I search for a trap there”). The key to memorization being repetition, a tabletop role-playing session is a perfect tool to get common sentence pattern effectively learnt.
It is like if the brain was deciding if an information was good enough to be stored in long term memory based on how much emotion it is charged with. People tend to remember quite vividly little details of situation where they felt deep joy, pain, or fear. I personally failed to memorize 攻撃 (attack/assault) that I used to encounter relatively frequently in the NHK news web easy articles until I associated it with being trapped in a cave with a hostile pack of Orcs.
Acquiring a habit of interacting with real people in your target language regularly, in the long run, is the most effective way to get closer to fluency. Doing so pretending to be a warrior on a quest for revenge against the evil wizard who enslaved your tribe is probably the funniest way to do so short of actually being in the country you are learning the language of, drinking beers and snacking traditional food with locals.