what is their mistakes?

Wrong: what is their mistakes?
Correct: What are their mistakes? OR: What are the mistakes of the following/below statements?

Wrong: desides stubborn, he is sometimes aggressive. (Chinese-English!)
Correct: Besides stubborn, he is also too aggressive sometimes. (Since " aggressive " could be positive, if you want to describe a negative meaning, " too aggressive " would be more appropriate.)

Wrong: I like to run and play football.
Correct: I like running and playing football. (Always use " -ing " for hobbies. More examples such as: swimming, bicycling, reading.....)

Wrong: Tsing Yi has a lot of wonderful places. (Chinese-English!)
Correct: There are a lot of wonderful places in Tsing Yi.

1. Besides stubborn, he is sometimes aggressive.

2. I like running and playing football.

3. There is a lot of wonderful places in Tsing Yi.

What ARE their mistakes?

Besides being stubbon, he is sometimes aggressive.
I like running and playing football.
There are a lot of wonderful places in Tsing Yi.

what 'are' their mistakes?
besides being stubborn, he is also aggressive sometimes.
i like to run and play football.
there are a lot of wonderful places in tsing yi.