Can I keep both my EB-5 green card and my marriage green card when both are conditional?

You cannot - the conditional green card through EB-5 would need to be terminated first.

You cannot have two green cards. You have already adjusted to a conditional permanent resident status based on an approved I-526 petition. Generally, you should have withdrawn your marriage-based case. Alternatively, you need to file I-407 to surrender your I-526 based green card in order to be eligible to adjust based on marriage. You should consult your immigration attorney.

You cannot have two green cards so you will have to elect. It will be interesting to see if they approve your conditional marriage green card application because you will definitely have to execute an I-407 surrender first. I always have the client apply for the marriage green card abroad and then have them surrender prior to the interview because to adjust status in the U.S., you ordinarily have to be in nonimmigrant status. Adjustment is not to move from one green card to another but from nonimmigrant to green card.

No, you cannot get a green card based on both categories. I do not know about the timeline of your case, but in general, you should have withdrawn your NVC/I-485 for the first green card before you file for your second green card. You should consult with an immigration attorney immediately.