In my company, we have more than 20 sites of sharepoint. However, we need to standardise all the top link bar in other 20 sites. Can I upload my html file for top bar link and override the default top bar link. I understand that I can manually can top bar link items but it time consuming. I am new in Sharepoint.
If all those sites have the same master page, edit it and add your html menu there.
Start here:
http://changecase.net/blog/2015/10/28/safely-customize-master-pages-in-sharepoint-2013/