완고하다 in English:

She's stubborn.

They have huge arguments because they're both so stubborn.

You are so stubborn. I told you to turn right. Now we are lost.

Facts are stubborn things, but statistics are pliable.

Stop being so stubborn and listen to what we have to say!

Your argument is not any more convincing than that of my stubborn father.

You must not be stubborn and should be friendly.

You were right, I was too stubborn. / Donkeys can be very stubborn. / Stubborn stains can be removed using a small amount of detergent.

I thought our boss was stubborn as a mule but actually he has his cute side.

Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.

A stubborn person is determined to do what they want and refuses to change their mind... his stubborn resistance to anything new.

Why are stubborn people so difficult to persuade?

That stubborn man in Prague has finally signed and we have now reached the end of the journey at last.

She always does what she wants, coz she's a very stubborn girl.

She's so stubborn. I bet if she ever gets reincarnated, she'd be a bacteria capable of living in empty space.