Which language do you consider hardest to learn apart from English?

Typically: Russian / German

The reality:  Imagine how Germans & Russians learnt it themselves ? Because they born with it & people spelled it over & over around their ear. Human own high powers & ability. Just think about the moment that all the languages been invented. Human brain is so powerful,strong, & flexible. Humans can learn anything they want, (apart from basic talents & two side of brain ect . .) if humans don't get lazy themselves, build their confident, stand under the pressure of learning, don't give up & continue forward. Practice properly. They'll eventually learn it. Anything that they want. So no language is hard to learn, it only comes hard when we don't wanna be strong enough to challenge ourselves.

I would imagine Arabic would be hard to learn as it can be composed of guttural sounds that encompass many of the prefixes and suffixes , so being able to pronounce words what be rather daunting, add on with the different dialects of each region and it might become even more confusing.

Another hard language would Basque, as I heard that often alternates from French to Spanish so for that language any none native French or Spanish speaker would have to learn two languages and then process when to appropriately differentiate from the two .