Toki Pona: an attempted universal language with only ~120 words
I love Toki Pona and have been using it for a little while. You can check my YouTube channel if you wish to see/hear it live in action: https://www.youtube.com/@janPolijan  
Toki Pona gives you the fun part of using a foreign language, but it skips the boring part of having to learn a ton a grammar and vocabulary. And the phonology is delightfully simple, so you won't have a bad accent. There's a growing and very active community around it and people write and share novels and songs. But it's also useful just as a personal language because it's really like a game for your mind. After a while, you reach proficiency and then fluency and it gets even better. It is absolutely possible to explain fairly complex things if you continue to push it. You obviously wouldn't want to do engineering in Toki Pona, but explaining quite complex topics is absolutely possible if you really desire (for example, someone has put a YouTube video explaining non-euclidean geometry in Toki Pona). One final thing: contrary to popular belief, Toki Pona is not designed to be as minimal as possible (the "tuki tiki" conlang with only 39 words modifies Toki Pona and pushes towards true minimalism). Toki Pona sure is tiny, but it's mostly designed to be fun and retain expressiveness.