Answer 1

Height =100% don't works if parent tag has no fixed height.
You should use height:100vh ;
for .image and .overlay

If you want overlay of color over image you should see this code you can set mix-blend-mode: overlay;

css page line 7

and check here.
bydefault it is screen.

https://code.sololearn.com/WglqI850ZImr/?ref=app