Hey joanna, Thanks for using our Education WordPress theme.
If you want to remove background color which overlap the background image on title section with low opacity. Opacity is set 0.8 while 1 is solid color and 0.8 means 20% low color. If you want to change opacity follow this CSS just change .8 to any number you want like .6 or .1 to get solid color use 1 without any point.
.title-section {
background-color:rgba(27,27,27,.8) !important;
}
And in case you want to remove background or overlapping color completely then use this CSS
.title-section {
background-color:none !important;
}
To add css go to wp-admin >> Appearance >> customize >> Additional CSS
If you are asking about something else please elaborate your question more thanks.