Dad Lent Uncle Money, Uncle Doesn’t Return

long story short, my dad is currently living with me in a “rich” country while my uncle currently resides in a “poorer” country (my dad immigrated to our current country)

a few months ago, my dad lent my uncle $5000 (in dollars) which is considered a lot of money where my uncle lives to help with my uncle’s business. however, as you can probably guess my uncle refuses to give him back the money which i think is really unfair since my family lives in one of the most expensive countries in the world, and we need to money due to us buying a new house.

is there a way my dad can sue my uncle for the money even though they live in different countries? my dad has messages of the “loan” and pictures of the transaction.