“Can / could I borrow your car?”


“Yes, of course you can.”

            (or)

“No, I am afraid you can't.”

1. “Can I help you?”  


“Yes, thank you.”

                (or)

    “No, thank you.”  

2. "What can I do for you?" (or) "How can I help you?"

   "Yes, I'd like a reservation to Chennai."

 "For How many people?"

    "Ten people."

3. "Excuse me. Good morning."

    "Good morning. Can I help you?"

     "Yes,  I'd like a reservation to Chennai."

Note:

I'd like = I would like = want

Request                                  

1.  "Can / could you post this letter, please?"

    "Sure / Certainly / Of course / Yes, of course."

                       (or)  

     "I am sorry I can't."

2. “Can / could you lend me Rs.10?”

    “Yes, of course I can.”  (or) "Sure."

                  (or)  

   
“No, I am afraid I can't.”  (or) "I am sorry I can't."

 3. "Excuse me, Could you tell me how to get to the bus station."

    "Sure. Keep on until you get to the church.
Turn left at the church.  Go past the petrol station.
It'll be on your right."

                       (or)  

  
     "I am sorry I don't know."

4. "I wonder if you could help me with my bag."

        "Sure." 

                   (or)  

 
"I am sorry I can't."

"Both can You? and could You? Can be used for request.
But could is the more polite."

Suggestion

“Could we meet tomorrow?" (or) "How about meeting tomorrow?" (or) "I was wondering if we could meet tomorrow?" (or) "Let's meet tomorrow?" (or) "Let's meet tomorrow, shall we?"

“Okay / Sure.”  

            (or)  

“I am sorry but my schedule is booked up tomorrow.”  

To express condition

“Could you run the business by
yourself?” (if you tried)  

“Yes, I could.”  

            (or)  

“No, I Couldn’t.”  

He can't be still working there.

He could not have done it by himself.