I want to change the font for the website:
I tried to use plugin but the plugin does not work in menu and headers
tell me how to change the font type in all sites and headers
You can set up font for whole site in Customizer > Typography:
If you want to make the change for special section, please tell me so i can give you the css code to do it.
My font is not in the list I drop down but i did not found my font
my font is "trebuchet ms"
You need custom code to add more font if you want for the site.
You should find a developer to help you customize the function and control it.