You say it in English, just as you would do in the US or any other English speaking country.
You can say "സുഖാലി അധ്യാപക ദിനാശംസകൾ" (sukhali adhyapaka dinashamsakal) in Malayalam to wish someone Happy Teachers' Day.
행복 한 교사 하루 = happy teachers day
In Tamil, you would say "இனிய ஆசிரியர் தின நல்வாழ்த்துக்கள்" (Iniya aciriyar dinna nalvazhthukkal) to wish someone a happy Teacher's Day.
Simply say "Happy Mother's Day."
Happy independence day?
happy name day
Happy Friendship Day.
happy fathers day
happy mothers day
You say happy valentines day. We speak English too.
Happy day mom or can say nice day mom
You mean "Happy Valentine's Day"?