{{ entry.image.first().url }} won't show image

I am on my first Craft CMS test site. Have some problems showing a simple image.

<img src="{{ entry.hero.first().url }}" title="{{ hero.title }}">

I get the title but can’t get the URL. The src attr is always empty. Tried a couple of variants like:

• entry.hero.first().url()
• entry.hero.first().getUrl()
• with and without ()
• etc.

But entry.hero.first().filename gives me "my_testfile01.jpg"

I can’t see what is wrong.

File is local with path set to "./"
Image field has no sub path.

MAMP (Apache + PHP 7)