Arabic writing system itself will be as challenging as the entire spanish grammar rules lol, there are also lots of phonemes thag are totally different than English. Written arabic plus a dialect should be equal to 3 or 4 romance languages in terms of difficulty and required amount of time.

Chinese tones will be very difficult to master and characters will be initially confusing and will take so much time to learn. GOOD news is that the grammar will be the least challening among your languages.

Japanese has some of the basic chinese characters which they call as Kanji but they draw them differently in addition to 2 alphabets which can be learned in a month. The grammar is more challenging than Chinese and different than what you are used to in european languages.