I seems very strong in appearence but actually very weak inside my heart
strong坚强的,强壮的firm坚强的,结实的staunch坚强的,可靠的sturdy坚强的,坚定的e.g.strong determination坚强的决心firm leadership坚强的领导sturdy fighting comrades坚强的战友strong will坚强的意志
He is a man of strong will and courage,daring to challenge the unknown.
he appears strong and stubborn,but is actually quite fragile in his inner world.
or
he appears strong and stubborn outside,but fragile inside.
I am a petite appearance,the heart is very strong girl