I recently upgraded to the newest version of the Blogger and noticed that after the upgrade I had duplicate menus appear. The issue can be seen on my website: https://filteredthought.com or via screenshot here: https://imgur.com/qB5Y9mw.
Hi, You can deactivate all your plugin and check it again.
Please check your menu part as well. It can not happen itself. Might be a third-party plugin. Please remove unnecessary items from the menu.
If you still struggling, go to dashboard > settings > reading > choose
Your homepage displays: your latest posts and save it.
Thanks