Hello @Nima-DE
it's not support to: https://docs.microsoft.com/en-us/sharepoint/dev/solution-guidance/portal-branding
What not to do
The following list contains the key things not to do when you apply branding to your portal.
Don't:
- Override branding of the Office 365 Suite Bar.
- Customize branding for personal sites.
- Implement by default your custom branding by using custom master pages.
But if you do want to do it, maybe this will help:
https://docs.microsoft.com/en-us/answers/questions/326418/how-to-remove-the-34sharepoint34-header-na...
My througts about the SharePoint start site:
Work with this site, it's a good overview for your users, and this are the informations, that will be appear in your SharePoint App Bar, so, let the link and train-train-train your user's.
Regards, Dave
