Hi, I understand there is a guide (found here: https://mdbootstrap.com/education/wordpress/theme-3/) to implement mdbootstrap to create a new theme but how do you implement it into an existing wordpress theme? 

I have already built my website using the "twentyseventeen" theme and would like to intergrate some of the functions  from mdbootstrap such as database tables onto my website.

Since the functions.php already existed in the theme directory, I added the needed functions to the bottom of the existing functions.php file:
/**
* Include CSS files
*/
function theme_enqueue_scripts() {
wp_enqueue_style( 'Font_Awesome', 'https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css' );
wp_enqueue_style( 'Bootstrap_css', get_template_directory_uri() . '/css/bootstrap.min.css' );
wp_enqueue_style( 'MDB', get_template_directory_uri() . '/css/mdb.min.css' );
wp_enqueue_style( 'Style', get_template_directory_uri() . '/style.css' );
wp_enqueue_script( 'jQuery', get_template_directory_uri() . '/js/jquery-3.3.1.min.js', array(), '3.3.1', true );
wp_enqueue_script( 'Tether', get_template_directory_uri() . '/js/popper.min.js', array('jquery'));
wp_enqueue_script( 'Bootstrap', get_template_directory_uri() . '/js/bootstrap.min.js', array('jquery'));
wp_enqueue_script( 'MDB', get_template_directory_uri() . '/js/mdb.min.js', array('jquery'));
}
add_action( 'wp_enqueue_scripts', 'theme_enqueue_scripts' );
?>

The current errors I am receiving in the console are:

Failed to load resource: the server responded with a status of 404 (Not Found)
mdb.min.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
style.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
/database/css/addons/datatables.min.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
popper.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
jquery-3.3.1.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
mdb.min.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
bootstrap.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
mdb.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
datatables.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
style.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
/database/css/addons/datatables.min.css:1 Failed to load resource: the server responded with a status of 404 (Not Found)
jquery-3.3.1.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
popper.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
bootstrap.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
mdb.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
datatables.min.js:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
(index):172 Uncaught TypeError: $ is not a function
at (index):172
mdb.min.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
bootstrap.min.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
style.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)
datatables.min.css:1 
Failed to load resource: the server responded with a status of 404 (Not Found)


Is there an existing wordpress function within functions.php which I need to change in order to get this working?