How to create a Search API block? I have a search view based on "Search API", I want to replace the default search block of the drupal core with a block "Search API".

1) How to modify the search block of the heart so that it uses search api instead ?

or

2) How to create a custom block /structure/block/block-content to use "Search API" ?
You should create an exposed filter for the View page, probably based on the full text search field, and then set the filter form to show in a block.

All can be done from within the Views UI on the edit form for the search page.