@DebbyNPL - If you need to correct data that's already been collected, I'll point you to the Data Repair API. This approach will change the actual data stored on Adobe's servers.
Another option might be to use Classifications on the variable so your reports only show the information to the left of the "?". This approach is flexible in that it does not alter the actual data stored on Adobe's servers. It simply lets you build an alternate or more appropriate view. Another benefit here is that Classifications can be modified as many times as needed should you need to make additional or future adjustments.
Beyond modifying or Classifying data that's already been collected, I recommend correcting the data collection issue that caused this problem in the first place. Whether it's a coding issue or that the URL had more than one "?", it's best to make sure you're collecting clean data from the start.
