A.Can you give us? (Correct)

 Can you join us?  (Correct)​

 Why don't you play with us? (Correct)​

B.Oh, my tube. Can you help me? (Correct)

=> Corrected punctuation.​

 I'm sorry ,I can't swim. (Correct)​

Don't worry . I can swim I get give it  --> Don't worry! I can swim. I can get it.

=> Corrected: The sentence is corrected grammatically.​