right, we all know how crafty the japanese are - they, under the pretense of politeness ask you
“Nihongo ga ojozu desu ne?” in hopes that you’ll say something like
“Hai, domo arigato gozai masu” and sound like a jerk.
Usually, the only way to answer to this challenge is with a self-demeaning
“Iie mada mada desu”
“Iie mada jozu ja wakarimasen”
however, stead of doing that how about saying something more clever like
“iie chigai masu. Watashino nohongoo tottemo akan desu yo”
that’l teach them japs!