I know, it’s silly, but i really don’t know at this point.
I tried to create a new folder in the frontend and had a structure like this
themes test assets css bootstrap.css (i took a css file that contain bootstrap 4.1 and have in it a theme from bootswatch.com) views layouts main.php (i copy it from views folder and added use frontend\themes\test\TestAsset with the change of AppAsset::register($this); to TestAsset::register($this);) TestAsset.php (i copied the content from the AppAsset file)
In config -> main.php i added
'view' => [ 'theme' => [ 'pathMap' => [ '@app/views' => '@frontend/themes/test/views' ] ] ] ],
The theme that i wanted from the bootswatch.com was applied (it made a mess from the navbar, img-thumbnail and caption class), but i was thinking i could just edit them and it will be ok. Every change that i try will not apply, not even the body background-color.
When i needed to add something, a class of my own i used:
and it was ok.
At this point, I don’t know how to edit the css of the yii2 or how to add another one that i could use and personalize.