How do I set up two meetings but let participants choose which session to attend?

Hi sayedsediqi, I would suggest using Channel Meetings. Schedule two Teams Meetings in a Channel. In the subject of each Channel Meeting, you can include the planned language of the Meeting. Each Team member can decide for himself to join the English or French meeting. 

When you start the Channel meeting, every Channel Member will get a toast message about the started meeting. If your users would like to be notified in Outlook, they have the option to get a calendar entry. To do this, the user open the Channel meeting details and in the left upper corner is an option to store this meeting as appointment in the Outlook calendar. Of course, this solution requires that there exist a team with all attendees.