Hi!

so...my first language is Persian and my second one is English,I'm a bit familiar with Korean and french, therefore I don't have a problem in terms of learning the grammar of either Chinese or Japanese, and I'm okay with writing the letters so it's all fine, but...
the problem is that Chinese uses tones and I'm afraid I would mess it up, and I started the basics yesterday, like hello, goodbye, counting and ect and ended up with a sore throat!
I'm an interior designer, a tour leader and soon to be a dress designer, so I want to know which is best for me to learn because apparently I don't have the ability to choose😐
Sorry for the long note!

Thank you in advance!

It depends on the people you intend to meet and the places you intend to visit.

Basing it on the number of world wide speakers, Chinese wins. You do realise that there are two forms of Chinese Mandarin and Cantonese. There are also various dialects. Not being a chinese speaker or much of a foreign speaker I have no idea if mandarin and cantonese speakers can understand each other. My undertsanding is if Chinese is similar to many other languages it is accent and inflection (perhaps the occassional word) that is different. Good luck with whatever direction you choose

Colin