As someone who’s learning a third language and also teaches English, I think a lot about approaches to language learning. When learning another language, I think it’s super important to set what fluency means to you. It’s a very vague term. When we think of fluency, you probably think of a native speaker. But then, that’s vague too.
I think a sweet spot is being as fluent as an average high school student. Although, it’s possible to have meaningful conversations even before that level, like say the level of an average junior high/middle school student.
Many European languages (including English) are rated on what’s called the CEFR scale. The CEFR scale is scored as follows:
A1-A2 (most basic/upper basic) (about N5-N4 on Japan’s JLPT scale for foreign Japanese learners)
B1-B2( Intermediate/upper intermediate) (N3-N2 on JLPT)
C1-C2 (Advanced/Advanced with academic mastery) (N1 on JLPT)
My estimates are really rough so take it with a grain of salt, but on this scale, B2 is generally the minimum needed to have a meaningful conversation with someone in your target language in my experience. I feel like B2 is about the level of someone about to graduate middle school. So when learning another language, don’t beat yourself up if you’re not as fluent as an average adult- you don’t need to be. Most native high schoolers are C1 at their own language. That said, if you really love a specific language and you want to get really good at it or you have a practical reason for doing so, then by all means, go for it!