foolishly, stupidly
Tontamente imaginé que él me ayudaría.
I foolishly imagined that he would help me.
Estás siendo tontamente romántico.
You're being foolishly romantic.
— स्वदेस (2004)
No te rías tan tontamente.
Don't laugh so foolishly.
— Victoria (2015)
Me reí tontamente.
I laughed foolishly.