Hello, @Delal,
You can find all the settings related to Typography/Font under Theme Options listed below:
Theme options > Typography.
Theme options > Header builder > settings of header elements.
XStore > Custom fonts > Upload Your Custom Font
Theme options > typography > headings
Check this topic https://www.8theme.com/topic/responsive-headings/
https://www.w3schools.com/cssref/pr_font_font-size.asp
https://www.w3schools.com/cssref/pr_font_weight.asp
https://www.w3schools.com/cssref/pr_text_color.asp
Regards 8Themes Team.