What do I do after I have a b2 visa, overstayed for 7 months and got married with a citizen?

You should file the I-130 AND the I-485 if you entered the country lawfully and can prove that lawful entry. Until you file the I-485 you are subject to deportation because the filing of the I-130 alone does not grant you any status.

You can apply to adjust status based on your marriage to the US citizen right now. I would suggest you meet with an attorney who can help you in filing a one step adjustment of status application. Even if ICE puts you in removal proceeding. before you have a chance to file the petition, you will still be able to adjust status in removal proceedings by proving you are in a bonafide marriage with a US citizen.

I cannot advise you to ignore the lawful request of an officer of the United States. Instead, you should immediately hire an experienced immigration attorney who will help you in negotiating the terms of your surrender. If at all possible, before meeting the officer you should immediately file your I-130 petition with CIS and have a copy and proof of filing which your lawyer will give the ICE officer. In terms of your eligibility to adjust, even if you overstayed by 7 months, it will not bar you from getting a green card, if you are otherwise eligible as long as you entered US with a B-2 visa and you are spouse of a US citizen,

You definitely need to hire an attorney. If a notice to appear (NTA) was issued you must appear before the court. Submit the petition for alien relative and adjustment of status as soon add possible.