What I have to do to get married?

You should have your BC, passport, entry and status docs in US, and evidence of your good faith marriage which includes cohabitation, commingling...

I am the petitioner, will like to withdrawn pending i75?

You can proceed as you wish and your spouse will need to file for a waiver of the joint filing requirement for the I751 based on divorce and a good...

I make a mistake on my I-485, how do I format the letter to the USCIS to make the correction

You may correct the error at the time of interview without issue.

How do I answer this RFE ?

No it means you should send the Tax Return or transcript for 2018, not just the W2.

When can I expect my Greencard

You may contact USCIS directly though infopass, calling or making a written inquiry.

Can I get another citizenship while holding a green card?

This should not impact subsequent application for US citizenship if you continue to maintain eligibility.

Re: Birth Certificate for Parents petition?

You may submit now but the BC will be requested, delaying your case in any case.

U visa ?

It is taking 4 years for U visa processing at this time given high volume and limited number of visas available.

How do I go from having a green card given in 2017 to Gaining citizenship if I previously had a uvisa in 2015.

Yes it is 5 years but if you were married to USC for those 3 years as LPR then you could apply sooner.

Unfortunately he would need to wait the 12-14 years until the visa is available as all other applicants.