1. Generally, the cash withdrawal amount does not exceed 50% of the credit line, so your cash withdrawal amount is 10000 yuan, and the existing credit line in the card is 18940 yuan. Basically, it can be judged that the credit line of this card is 20,000 yuan. You said that the available balance is 2000 yuan, which should be wrong. I infer that the withdrawal limit on ATM may be 2000 yuan.

2. If the credit line is 20,000 yuan and the current credit line is 18940 yuan, there is still a deficit of 1060 yuan today. However, if the arrears are overdue or withdrawn, the amount of arrears will change due to the penalty interest. Some expenses, such as late payment fees, are not generated in real time, so you should save more before repayment.

3. 5500 yuan deposited three days ago, because it is a credit card repayment, not the same day, can only be included in the credit line the next day. Therefore, when you repay the credit card, you need to check whether the available amount has increased by 5500 yuan, and you will know whether the repayment has been successful.