Here are some suggestions for self study, but you will need to become your own teacher. Some of this you will know, and so forgive me if I am trying to teach my granny how to suck eggs.
For a quick start, don't even try to write. Remember that there are many people around the world who can function in business who are illiterate.
Social Chinese will help you a lot, and business Chinese is for advanced learners.
Most books will start you reading using Pin-yin (Romanized notation) but move you up to reading Hanzi (Simplified Chinese Characters) before you get through beginner level. This I found to be a major barrier. The same is true for many online courses.
You can learn to read, without having to learn to write. You can be semi-literate.
I can recommend Pimsleur Mandarin I-III audio. It is expensive, but lots of very naughty people download it free from the internet. This is very naughty and should never be done (snigger). Pimsleur has a good mix of social and professional Mandarin. Level III will take you to intermediate level, without the need to learn to read Chinese characters.
Getting a Chinese teacher also helps with the audio courses, as they can help you practice your pronunciation. Pronunciation is critical in Mandarin, change the way you say a word and change its meaning. For example, to the untrained ear the words for 'buy' and 'sell' sound identical.
Another advantage of a teacher is that they know the vocabulary that you will know, for your level. For example a beginer will have a vocab of about 600 words at the end of the course. Most people you meet will use a full vocabulary, this is frustrating and demotivating.
Find yourself a friend, not a language partner. Ideally someone who speaks almost no English, but likes the idea of a western pal. Make sure it is someone you have something in common with. I talk my wife's driver about cars and sport. If you get a language partner you may spend most of the time speaking English.
You can go with a Chinese speaking person to the market to buy stuff. There is more than this to haggling. Once people know you are not a spy and want to practice Chinese you can speak about buying, selling, trading, transport, lead times, import and export (in the fruit market), supply chains; its not all about prices and haggling. It might also help to become boozing buddies of local traders (trading company).
BUT you will need to pre-learn essential vocab first. You will need to be your own teacher.
In short. My recomendation. Pimsleur audio, with occasional input from a teacher to correct pronunciation, don't try to read, and find a buddy who speaks poor English. Then find a buddy who speaks better English to trawl the markets and befriend some local businessmen.