Depends on your age and what languages you can speak I guess. I guess the easiest language to learn for a native English speaker would be Romanian as its a Romance language. Slavic languages are really difficult for anglophones to learn.
Discussion
I know some basic Russian, and my wife learned it at school, which used to be useful, before the Russophobia really kicked in. Not a problem in Russia itself though. 🤔
Not a problem in most of the world. Apart from Baltics, Poland, Ukr CEE countries have neutral, mixed, or positive views.
Well that's an advantage then. Perhaps go to some places on holiday, see where you like and what you can understand. Bulgarian uses Cyrillic but they also use words from other languages so they say ciao and merci. Things are also very cheap there so perhaps having a larger property can be advantageous even if things get worse there too for whatever reason.