I know that many English native speakers have problems with the strong "z" in German and tend to pronounce it like "s". The Chinese learners are very good with the pronunciation of the strong “z” in German, as long as you give them the right equivalent in the Chinese language. So I often tell them that German “zu” is pronounced like “Chinese vinegar”: 醋 “cu”!
What are the sounds in the language you learn you are struggling most with? What are your methods to solve it and produce the right sound instead?
Well, I'm learning English, so vowels, of course. Especially [i] / [ee]: it's a very common mistake to confuse them I believe. But! Some time ago, one person told me that [ee] stands for Russian [и] (more or less) and [i] is actually something between [и] and [э]. That's a very rough approximation but it helped me a lot I think. If you're by chance reading this - thank you so much!
Plus, a few months ago another person here on Italki told me that I mispronounce consonants as well - and yes, since then I've been able to hear it too. In Russian pronunciation, all voiced consonants at the end of the word are pronounced like their voiceless counterparts most of the time, so [d] becomes [t], [v] becomes [f] etc. (ave consonant assimilation!). And... It doesn't work this way in English, as you probably know. However, it's really, really hard to pronounce voiced consonants at the end of some words for me, and I constantly forget that I make this mistake. The moral of the story: learn pronunciation first or you'll have to relearn everything all over again.