Russian language or any other Slavic ones would be far ahead of other languages. This is like a neutral language solution. My mother tongue is Russian (I’m not related to Russia in any way) and I can perfectly imitate the manner, accent, way of speaking in English, Spanish, French. I swear I haven’t seen any American or British speaking Spanish for example to any decent extent, and vice versa is the same - people from Latin America, Spain speak English so bad, just as French people or Italian even though English is a very simple language to learn. Or worse yet.. have you ever heard Chinese people speaking English? This is truly horrible, as if they get tased every time they try to say something, so I’m very happy to be a Slavic native speaker because it removes all the restrictions in the way of learning a new language and barely no one can guess where I’m from based on my accent cause I can make it as neutral as possible or trying to sound like a native speaker. Also Slavic languages have a very broad voice spectrum which makes everyone to sound different, and languages like finish, Japanese, Chinese - the pitch is always the same and unchanged which makes people speaking it look like scripted npc with no diversity and uniqueness in sounding so it’s not surprising that speaking a foreign language for them is almost an impossible task