What is the most useful foreign language to learn?

You should choose the best foreign language to learn according to your goals.

For example;
If you are a busy trading company and you are busy with the Asian market: Chinese

If you are in the energy sector: Russian

Wherever I go in the world, if you agree to one of 2 people, you say: Spanish

If you want to be among very special people, one day I can earn good money if you work, Nordic languages.

If you say I will benefit my automotive and industry sectors: German

If you are interested in music (especially classical) and art: Italian

It should also be suitable for the profession you do or plan to do.
Let’s say you have studied engineering; you have to research and look at which country gives the most jobs to engineers.

Choosing to learn the language of the country in which your mother tongue is most needed also guarantees that you will not be unemployed in that country.

It is also useful to learn the language of the country you plan to live in the future. But there is no need to know Chinese to live in China, and not to speak Hindi to live in India. English is quite enough in these countries.

So, know the prevalence of your own language in the country you plan to live in so don’t waste your time and money to learn a language. In such countries, sometimes even a few foreign words work for you. Learning a foreign language can be easier with some applications. Although it may seem like children, even Muzzy foreign language may be enough for simple exercises.

Source: eksisozluk.com