Fastest? Moving to a Spanish speaking country. Total immersion is how the French Foreign Legion teaches French from my understanding.

I would probably do a mix of a language program, say Duolingo, Pimsler tapes or Rosetta Stone, and asking a few of your Spanish speaking friends to speak primarily Spanish to you, switching to English only when you are completely lost on a concept. Between the two you should pickup Spanish or rather, their dialect of Spanish, fairly quickly.

The quickest way is probably complete immersion, but I’m guessing that’s off the table. Second best would likely be one-on-one tutoring.

Some great suggestions already, also consider flooding your entertainment with Spanish. For example if you were a big fan of the office and know all the episodes, try watching the whole thing with Spanish dubbing and subtitles. Immerse yourself as much as you can

THE best way would be to go live in a spanish speaking country The second best is getting a latino girlfriend The third best is geting yourself a private tutor.

The cheaper the way the longer it takes.

Laziest fast way is to watch a ton of Spanish speaking movies with Spanish subtitles

I’ve learned many languages from many sources, and rosetta stone is the fastest and the most comprehensive.

you can move at your own pace, they have audio, written and reading positive reinforcement, speaking exercises, it’s pretty fun overall, and extremely practical and encouraging.

it is also by far the most premium experience, nothing else comes close.

you can tell the devs and linguists put a lot of work into developing the course and it really shows when I compare it to any other app or program I’ve used.

Spanish was one of the first languages I learned, and I used Rosetta stone for it and can testify that spanish in particular is fantastic, although I haven’t really come across a Rosetta stone course that isn’t highly effective.

for when you’re walking around or you don’t have a lot of time to sit at a computer, pimsleur audio courses are the best runner-up

they’re amazing for training your ear to acknowledge foreign languages and feel comfortable with unfamiliar cadences and speeds.

either one will help you get used to the language, but you will learn more words and phrases quicker with Rosetta stone; it’s the best language program out there.

Live in spain

Use it as much as possible and don’t be afraid of making mistakes.

Don’t bother with course materials I would say. Just speak Spanish with them as much as you can. Maybe watch a few Spanish-language tv shows, especially some intended for kids (Sesame Street?) since those usually have clear pronunciation.

Really the first important thing in a new language is to train your ear to break down the sounds of continuous speech, so it sounds like words instead of mush. That takes some tens of hours to get traction at all. So do lots of passive listening with your coworkers. Stuff like grammar and vocabulary come next and can be gradual. Course materials can help with grammatical subtleties but basic speaking and listening come first.

Also, try to quit speaking English quite early if your coworkers will put up with it. Speak Spanish and use a dictionary if you don’t know a word. Don’t bother with flash cards. You’ll forget stuff and have to look it up again and that’s fine. After a few repetitions it will stick.

Try to make your pronunciation very accurate. That will help in all areas. We think of phonetics, vocabulary (lexicon), and grammar as separate things, but they are all interrelated and mutually reinforcing.

You will find yourself thinking in Spanish instead of English pretty quickly. You are basically reformatting your brain so just roll with it.

Be aware that your English can actually get worse from this process. At least mine did. Decide if you are ok with that.

You can have conversations with offline text gen AI models. They are usually fluent in many languages. It is not a great primary source but you can treat them like a private tutor that can answer your specific questions and it can point you in the right direction.

Picking up a 2nd (or more) language is just going to be hard. There’s not a magic shortcut, or anything you can buy or course to take that will make you fluent in a month.

That out of the way, there are lots of resources out there!

Look up comprehensible input channels on YouTube (eg, Dreaming Spanish). You can find something at your level, even down to the point where they’ll mostly point at pictures and say words. Eventually add in things like cartoons, news, podcasts, or social media when you feel up to it.

There’s debate about whether you need anything besides input. I’m partial to a mixed approach, so I’d say get a good textbook too.

Anki is great for vocab flashcards (but you’ll have to find decks, which can be annoying). Apps like Duolingo can be a good supplement too.

Make a habit through the day or thinking about how to say things in Spanish. Repeat your sentences in your head, or think about what the Spanish version would be of signs you see.

It’s just a long term goal though, to get anywhere meaningful. Engage with your target language every day.

Learn a hundred words,

The most common ones, or the ones that are most relevant to your vocation.

Use them incorrectly and ask “como se di-se” (how do you say) to those who are multilingual, or trying to learn English

Spanish is my native tongue, so this might not work as well as I expect it to, but Pimsleur courses are GREAT to get quick phrases and learning to think in the language. They try to teach you very close to how native speakers learn it, and because of the repetition you tend to remember most of it.

That being said most of their content is focused on visiting a different country, so you might not need the very basic phrases like “I’m American, I don’t speak <language>”, but they give you an idea on how the language is structured.

Finally, while Pimsleur and many other suggestions here are great, it varies from person to person so you might need to find what works best for you.

Tell your colleagues you’d like to learn their language and ask if there’s someone willing to correct you and endure you talking their language badly. Then get to learning in the best way you can and practice with them.