Mandarin Chinese

A good way to kill two birds with one stone is to join a language exchange site like www.italki.com
There you can exchange languages with many Chinese students of all ages. You can contact and message people directly, no fees, unless you book a Chinese teacher or tutor. I teach English there, and have had 800 students, half of whom are Chinese, and some are good and long-standing friends. It is a site for all languages, but understandably many are Chinese from all over the world, including Europe.

Just be aware it is a genuine language exchange site, not a dating site.

Immersion. my boy, immersion. Working on my fifth language, starting with Duolingo. Decent free platform, which takes one up to conditional subjective tenses. But it can only provide the 500-1,000 word basic vocabulary, which linguists know actually can take us pretty far.Then simply spend time living in the linguistic culture..Avoid anyone who isn't fluent in the language of interest, and listen to radio/TV, read papers, and so on. A GF ain't a bad idea, if she's hip. I once had such ideas for Mandarin, of course as a world tongue, but also to explore ancient texts on TCM and acupuncture. One party state's evolution sort of turned me off. Gotta master the ideogreams, my friend, at least on a basic level, for full effect. Otherwise you'll come across like the typical American high school foreign language teacher. Or worse, as one of those pathetic ESL dilettantes .

No it is by no means a difficult language, grammar is much much simpler than English. I have to explain the nit-picking 'nuances' of English to Chinese students tenses conjugation in terms of their grammar; English is for a learner overloaded with synonyms and shades of meaning, with phrasal verbs and prepositions. The disconnection between spoken and written form, the absence of an alphabet however are certainly issues.