Deleting cookies in Firefox
Click on the menu on the far right next to the address bar (the three bars on top of each other). Choose Settings – data protection and security. Click on the heading Delete Cookies and Website data and then click on Delete. Then make sure that Cookies and Website Data is activated and then click on Delete. All cookies will now be deleted. Next click on Delete All Cookies. A confirmation window will open. After clicking on delete now all cookies will be deleted.
Here you will find further information on how to deactivate/block and delete cookies: https://support.mozilla.org/de/kb/Cookies-Blockieren
Deleting Cookies in Microsoft Edge and Internet Explorer
Click on the 3 dots in the right hand corner of the browser window or use the keyboard combination [Alt-X]. [Alt – X]. Choose browser History from the menu. Then click on Delete History. You will see a window to delete all data saved by the browser. To delete just the cookies remove all the ticks except for Cookies and Saved Website Data. Now click on Delete. This deletes all cookies. You will find more details on Deactivating/Blocking and deleting Cookies in Internet Explorer here: https://support.microsoft.com/de-de/help/17442/windows-internet-explorer-delete-manage-cookies.