There is no normal with a Motion to Reopen. If the documents submitted clearly show the error, then I would not expect it to take that long. If USCIS now has two sets of conflicting assertions, it is not so clear to make a decision quickly. If you are not happy with your attorney then absolutely you should at least get a second opinion and then decide whether to change attorneys.
Depending on the circumstances, it may take some investigating. Talk to your attorney for updates on your case. If you are not satisfied, you can seek a second opinion from another attorney.
What you are saying is somewhat confusing. If USCIS erroneously denied your I-485 then you would need to file a motion to reopen or, if the circumstances permit, refile a new application. It is unclear what you mean by "continue my case" since there would be nothing to continue if it was denied.
Processing times for motions to reopen can vary widely. Your attorney should be able to explain to you. If you are not satisfied with your attorney then consult with another experienced immigration attorney to obtain a second opintion.
While this answer is provided by a Florida Bar Certified Expert in Immigration and Nationality Law, it is for general information purposes only and an attorney/client relationship is neither intended nor created. You should seek out qualified counsel to review your case and provide you with advice specific to your situation. Review Mr. Devore's Avvo Profile for more information about his expertise in immigration law and how to contact him to discuss your case.
Hello. The motions to reopen do take a long long time, unfortunately. You may want to consider either pursuing the motion further by following up or filing a new I-485. A decision to be made with your attorney. Best regards.