Can / Be good at

Point 1: We use can to show abilities.

1. I can play tennis.
2. She can speak Italian.
3. They can build a computer.
4. This dictionary can hold one million words.

Point 2: The negative form of can has three spellings: can not, cannot, and can't.

1. I can't go tonight.
2. She cannot speak German.
3. I can not get an internet connection.
4. My car cannot go very fast.

Point 3: The adverb well is used to show a high ability at doing something.

1. Can you speak Japanese well?
2. I cannot speak it very well. I can speak it just a little.
3. What can you do well?
4. I can cook fairly well.

Point 4: The phrase be good at means you can do something well.

1. Are you good at sports?
2. Yes, I am pretty good at sports.
3. Are you good at computers?
4. No, I am not good at computers at all.