Like always in life, the length and difficulty of your route is determined by the point of departure and the target to reach, because this is defining the obstacles to surmount on the way.

For a European, Chinese is considerably more difficult than Polish. For a Chinese, Korean or Japanese person it will most probably be the contrary.

And, as Sarah mentioned, for a native speaker of another Slavonic language, Polish is quite "accessible"

And there are also very personal preferences changing the game. When living in France, I learnt from my French friends about Breton, an extremely "difficult and exotic" language. When I tried it, it was the easiest language that I ever encountered: a beautiful language with clear rules and extremely few exceptions. On the other hand, when I tried Tibetan, I reached the point of unconditional surrender after three weeks...

Learning depends more on emotions than on our little brains, discipline and whatever techniques we might employ. There is that story of that guy, 15 years old, learning French at school. He has had 3 years of tuition and is not able to say a proper sentence. Then a French girl enters his life... and boom, after 3 weeks he is fluent in French... What would this guy have answered about the difficulty of learning French ... before ... and after ?

Arabic is not as difficult as it’s perceived to be. The reason it’s often thought to be difficult is that it has a lot of rules, but Arabic is so full of rules because, unlike English (and many other languages), its grammar is treated as a science. When it was standardized, many hundreds of years ago, the grammarians set out to explain and document everything. The point of Arabic grammar is to preserve the language essentially till the end of time, and the grammarians knew that at some point people would stop speaking it natively. And that’s exactly what happened: Arabs have stopped speaking Standard Arabic natively a few hundred years ago. People who have a natural intuition of the language tend to develop it like a language learner develops it upon reaching a near-native level of their target language.

In Arabic grammar there’s no such thing as “that’s just the way it is”. There’s always a reason for something. The question is whether one knows the reason or not. Even the exceptions have reasons. As a matter of fact, in Arabic grammar, the word for “exception” is the same as the word for “reason” (علة), because there’s no exception that has no reason. Exceptions and reasons are so inextricably tied that grammarians gave “exceptions” the same word as “reasons”.

I was once obsessing over a grammar point that wasn’t just an exception, but in fact an exception to an exception. I spent days looking for an answer. And then I found it, in a book written many hundreds of years ago.

What all this means is that Arabic is a language that was made to be learnt. Arabic was designed for learners. Because the only way to preserve a language once people stop speaking it natively is to learn it, and that’s the reason why everything in Arabic has been explained.

Arabic is not an easy language, but it’s a language that can be understood, not just memorized. And that makes it make sense.

If you fall in love with a Polish person and want to marry and share a life together it will be Polish that is easiest for you. You have a reason and a desire. If you fall in love with a Chinese person and want to marry and share a life, Chinese will be easier for you. 

Boy meets girl - girl meets boy = has always been the number one reason for wanting to communicate in a new language.

When love goes the desire goes. 

If you enjoy and have a reason to learn and learning is fun, you will overcome. 

Every fluent bilingual person I know, it has been love and marriage that has lead to the person becoming fluent. A wife or a husband is usually a better teacher than a teacher.