I also started learning languages back when I was 13, I’m 22 now (23 in July), so it’s been almost a decade since I’ve started. In reality, in not fluent in very many languages, but I just have ambitions to become fluent in a lot more. I’m also studying to become a foreign language teacher, so I’ve had classes in some of them as it was required. However, before I went to uni, I bought physical textbooks, used a crap ton of language apps (mostly ones for kids to start), used Rosetta Stone (which has issues cause it doesn’t use English at ALL, therefore you have to guess half the time, so I used the internet and searched up the difference between things and such), got physical games from said countries without English on it, played music, learned and decoded children’s songs, I also used iTalki, which is basically an online thing where you can click the language you want to learn, choose a teacher and have lessons with them over what you chose to learn. It’s really helpful! If you don’t have a lesson, your teacher isn’t available, and you still need answers to something, just post the question and someone will answer it, or, you can do what I did and assume the people already asked it, go online, search up the question and hope that there is an iTalki answer to it. They’re very trustworthy. I learned Czech, Korean, and Japanese from iTalki, and my brothers learned Japanese and Swedish from it. There is also a good app called HiNative, I love it! You can add languages you are learning and ask questions about them for others to answer. People tend to answer really quickly too. You are also able to give your feedback and help others out as well. It’s another one I recommend