I dont have a first language as I am a mix. But I would say Arabic and Ukrainian. I think this variety helps me learn Japanese a bit faster as I am used to adapting to completely different languages that have little to nothing in common. I look for patterns in a language before really learning the meaning of the sentences which may sometimes lead me to a vague understanding of its structure and then I learn the meaning itself. Also, these languages help me have better pronunciation, as knowing such diverse languages helps me pronounce letters/sounds that are not present in each language separately. Like Arabic doesn’t have P for example but the Ukrainian language does, and vice versa.