I can speak English.
My father cannot speak German.
Can you speak French?
My sister cannot skate.
Can you swim across this river?
I cannot drink this milk.
She cannot understand you.
Could you swim last year?
Last year I could not ski, but now I can.
Can (Could) you tell me how to get to the railway station?
Could you help me?
I cannot translate this sentence.
Nobody could help me.
Where can I buy bread here?
Could your grandmother dance when she was young? — Yes, and she can dance now.
I can use a computer.