Python!

Oh…oh, I get it. Learn Latin.

I would say that you already have enough on your plate and you should focus primarily on just one of your languages. But if you’re just looking to dabble, I think a South East Asian language like Mandarin would shake it up a bit.

Swede here, at school I learned both English and Spanish, I consider myself to be Swedish/English bilingual, but even after six years of proper in-school Spanish classes I have only a brief surface level knowledge of the language, it is about 20 years since I last took classes in Spanish, and I never used it outside of class.

My English however, I have used that daily for the last 20+ years, both at work and at home, over the years I have learned common expressions and slang, and have been told several times that I speak excellent English.

My point is that I would recommend prioritizing learning one or at most two languages outside of your native language, but learning them well, rather than trying to cram in as many languages as possible.

One thing that has served me well however, is understanding pronunciation of foreign names, pronouncing other people's names properly when other's wont bother to will grant you a lot of respect and help you work together.

I've always thought that learning the native language of a developing country would be a huge asset. Very few people do so, and outsourcing has a huge cost differential, so it opens up unusual career moves to capture that growth.

Hilariously, 12 year old me suggested this on the "what 3rd language would you like to learn" form in high school and somehow got in trouble for it. I guess they thought I was joking. Perhaps the joke was on them though, I immigrated to Vietnam and own a (small) tech company now.

Learn toki pona. Takes only a few days and pays off immensely.

That probably depends on your use case. But also what level are you on those other languages? How many do you think you can learn at the same time?

Japanese, get the most out of your anime and manga!

You must be some kind of savant to learn 4 languages at once. I can barely wrap my head around English.

Gaelic likely wouldn't be terribly useful but you'd be helping keep it alive by learning it

Klingon!

I just watched this video on toki pona. Really interesting in how it's easy to learn but the difficulty comes from trying to communicate complex ideas.

The ones that interest you the most will be easiest to stick with. I find things just through my general interests and poking around.

Favorite music genre? Listen to bands from different countries and see how they sound. TV shows, movies, and documentaries from other countries are another big one. Listen to the original language, see if it sounds interesting, maybe read a little about it.

Or maybe you know someone who you'd like to be able to talk with in their language. It could be anything. Pick one or two things to try and you'll get a feel for what you like.

I studied Norwegian bokmål a time ago and I liked unfortunately I had to stop

Catalan! It's a wonderful language.

Small shout out to !languagelearning@sopuli.xyz

Learning a European language, especially from a country that had colonised other countries will be useful. French and English, for the most part. Learning a romance language will also help if you were to touch Latin someday

I'd learn Mandarin next since there's a lot of speakers and Asia is a fun place. Japanese after that if I have the time. That would be my personal journey if I ever learn any other languages, but we'll see

I say French, it's a much more commonly spoken language than most people in the US realize, if you look at your food or chemical labels, you often see it's the second used language followed by spanish

Latin is very interesting, gives you the ability to read the original untranslated works of famous Roman historical figures and also helps you with nomenclature in science ( like for biology, medicine, etc)

Learn Arabic. I have started learning it too.

I found Esperanto to be pretty fun to learn. It only took me a couple months to get reasonably good with it so if you're looking for a language that's pretty easy and has a fun community then Esperanto is a good option.

Latin. I would have suggested it before you started learning two Romance languages.

I've been learning Norwegian Bokmål and it's pretty interesting seeing all the words that it and English have in common (as well as their differences).

Also, Toki Pona as others have mentioned. Might seem like a joke language at first, but the community is really vibrant and kind. You can make some real, meaningful connections through it. Plus, it takes maybe a weekend to get good at Toki Pona.