sudo nano /etc/apache2/apache2.conf
Find the following code inside the editor:

 
   Options Indexes FollowSymLinks
   AllowOverride None
   Require all granted
 
Change to:

 
    Options Indexes FollowSymLinks
    AllowOverride All
    Require all granted

After that restart the Apache server via:

sudo /etc/init.d/apache2 restart

Alternative: 

Alternatively you could replace all the contents in your public/.htaccess file

Options +FollowSymLinks -Indexes
RewriteEngine On
RewriteCond %{HTTP:Authorization} .
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]