[Grammar] Common mistakes in Grammar

[Stephen Appiah]

I would be very grateful if you could identify the mistakes committed in the following sentences
Yoon is a more competent instructor in korean than me.
I was surprised at you arriving late.
Thanks.

 

[bhaisahab]

I would be very grateful if you could identify the mistakes committed in the following sentences
Yoon is a more competent instructor in korean than me.
I was surprised at you arriving late.
Thanks.

Yoon is a more competent instructor in Korean than I am.
I was surprised at your late arrival.