Laravel App Launch in subdomain directory on shared hosting "htaccess problem"

A friend of mine installed this app on a vps and worked just fine, but installing it on a shared hosting there's a problem. the subdomain cannot be directed to public_html when created like on vps. we asked the hosting provider but nothing much they can do, they talk only about redirection.

The app folder is on root not on public_html. root/app/"all the files" wanna run it on subdomain /dashboard/ dashboard.domain.com domain.com/dashboard

.htaccess on public_html

<IfModule mod_rewrite.c>
    <IfModule mod_negotiation.c>
        Options -MultiViews -Indexes
    </IfModule>

    RewriteEngine On

    # Handle Authorization Header
    RewriteCond %{HTTP:Authorization} .
    RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]

    # Redirect Trailing Slashes If Not A Folder...
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_URI} (.+)/$
    RewriteRule ^ %1 [L,R=301]

    # Handle Front Controller...
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^ index.php [L]

</IfModule>

Must i edit this htaccess file, must i add a new htaccess in dashboard directory! if yes plz can you tell me what code must i use.