Since you indicated you retained a licensed immigration attorney who should be familiar with your particular case your best source of preparation in that upcoming interview is the attorney of record who could advise you correctly on any potential issues that must be addressed.
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It sounds like your lawyer did a good job getting you a second interview. S/he is the most familiar with your case and can advise you on what to expect at the interview. Questions normally focus on the validity of the marriage and the relationship.
Your lawyer did a great job ... stick with him/her and ask him/her these questions ... not strangers on a blog.
FORMER IMMIGRATION LAW PROFESSOR -- LEGAL DISCLAIMER: This answer is offered for informational purposes only. It does not constitute an attorney-client relationship.