Is the lawyer letter sent by Shanghai Pudong Development Bank serious?

Seriously. The lawyer's letter itself will not have legal consequences, just a warning. Lawyer's letter is regarded as a threat of litigation, which is a means for the parties to exert pressure on the other party to gain the advantage of negotiation and force the other party to make peace actively. The lawyer's letter issued by Shanghai Pudong Development Bank reminds users to fulfill their repayment obligations as soon as possible, otherwise they may be sued by the court.