The Foreign Services Institute (FSI) has developed a difficulty ranking of languages based on the time it will take an English speaker to learn the different languages. You can see the ranking here: https://www.state.gov/foreign-language-training/
It ranks the languages on their similarity to English. For example, Spanish and Swedish are in category 1, requiring an average study time of 24 weeks. At the other end of the scale are Chinese and Japanese, ranked category 4, and requiring a study time of 88 weeks.
Of course, there are variables – does the language learner live in the country where the language is spoken? Is the language learner a “natural”? Does he or she pick up languages easily? How much opportunity does the learner have to practice the language?
Over the years, I have studied a number of languages. My language learning experiences do not correlate to the ranking. For example, I spent five years studying German in school. German is category 2, which should take approximately 36 weeks to learn. I struggled with the grammar, and didn’t get beyond the most basic level, even though I enjoyed learning it and spent much longer than 36 weeks studying it. I found Japanese to be much easier to learn. For me, the grammar was a lot easier than German. I think it is ranked so highly because of its writing systems. There are three to learn – two can be learnt in a few days, one takes considerably longer. Another reason it is ranked as the most difficult is its honorifics, although if you live in Japan, you get used to these pretty quickly.
I am now studying Mandarin Chinese, another language ranked category 4. Having a background in Japanese is really helpful, and I am progressing at a satisfactory pace. In fact, I am finding it a lot easier than I find French, which I have been trying to learn for a while. French is category 1, and should be easy for me. For some reason, it isn’t. Maybe I just don’t dedicate enough time to it. Maybe I’m just not a natural when it comes to European languages. I also want to learn Russian and Korean. Russian is category 3, and Korean category 4. I have dabbled in both, and in the few hours I have spent on both languages, I have made much more progress in Korean, despite already being able to read the Cyrillic alphabet, and only having a basic grasp of the Korean characters.
Everyone learns differently. Everyone has different motivations for learning a language. Don’t let the difficulty ranking put you off learning a language you really want to master. If you have struggled with an “easy” language like me, it doesn’t necessarily mean you are going to find a “difficult” language impossible. You might be suited to the more difficult languages. Try it and see.