By default, Astra displays "Search Results For: [Keyword]" at the top of the results page. You can change this heading text easily:

If you want to change the text inside the search box (e.g., changing "Search..." to "Find what you need..."), use this filter:

: Navigate to Customize > Post Types > Search Page . Under the General tab, you can enable/disable the heading and edit the text in the Heading field.