Welcome to the Bunnings Workshop community @linglinghuai. It's marvellous to have you join us, and many thanks for your question.
From the cracks, it appears that a cement render has been applied over the bricks.
I'd suggest Selleys 180g Spakfilla Rapid Gap Filler would be sufficient for filling these cracks and holes. It's easy to work with and sand back to a flush finish. If you wanted to use something more robust, I could recommend Timbermate 500g Concremate Expanding Cement. However, getting a great finish with this might be more difficult as it is a harder setting product. Anything proud of the wall needs to be sanded back flush with it, and anything sunken needs to be filled. You can try tapping those coloured wall plugs further in the wall and filling over them. Alternatively, you can try to drill them out.