What happens if I am a derivative on an approved I-526 petition but I am about to get married with a U.S. citizen?

You can only have one I-485 going at a time, and if you are still eligible as a derivative (not aged out) I do not see why you would not proceed with the AOS through your mother. If you are concerned with the future viability of the project and being able to remove conditions, maybe going with the marriage is right for you.

If you are a derivative, you can drop off that petition and just apply for the green card through your spouse if you are sure this is a go.

If you marry a U.S. citizen, it will be best to apply for immigration benefits based on your marriage because to qualify as a derivative, you must be unmarried.

Your immigration status has no impact on the status of the principal applicant or immigrant petition. Hence, you can absolutely file any other immigration application without impacting the I-526 application. You simply do not filed adjustment of status application now that the case of your mother is approved. Just be mindful that you do not file your immigrant application with marriage to U.S. citizen until 90 days after you have been in the United States on your F-1 status. I do not know how long you have been in the country on F-1.

Your marriage-based green card application will not affect the EB-5 application of your mom as she is the petitioner. You can choose to just file the I-130 and I-485 as a marriage-based green card application.

You can apply for your adjustment through either the approved I-526 or the marriage case. Applying through a marriage case will have no impact on your mother''s case.

You can pursue your own AOS and it will have no impact on the I-526 of your your mom.