Hello Prisca,
Thank you for posting to community forum.
As I understand you have the questions about the folders in Quick Access in your OneDrive account.
These folders are the links to your organization SharePoint sites where you can collaborate with your colleagues. You may see an example

Generally, the Quick access Shared Libraries in the OneDrive for Business will be displayed based on the Frequent sites and Sites which are Followed. So, once you follow the SharePoint site or frequently go to a site, the Document Library will be displayed in the OneDrive for Business after some time.
So, you may go to this SharePoint site to check if it is your followed site now. If yes, you can unfollow it. Select SharePoint in your app launcher, click on the star icon to remove from the Favorites

If you are not following the site, you may wait for several days, and it may automatically disappear form your Frequent sites section. So, it will also disappear form the OneDrive navigation.
If you want to add these folders to your OneDrive sync app you can click on the Library and select Sync from the menu bar.
I hope this information was useful for you, please post back to us if you need further assistance.
Best Regards,
Igor