rebuilding/ rewriting a url to make it SEO friendly

You can create a rewrite rule using add_rewrite_rule() that will match a given path to query parameters:

function wpse_283774_rewrite() {
    add_rewrite_rule( '^events/([^/]+)/?', 'index.php?pagename=events&country=$matches[1]', 'top' );
}
add_action( 'init', 'wpse_283774_rewrite' );

This rule will match whatever is after /events as the country query parameter. Setting the third argument to top means that it will match our rule first, otherwise it will try to match whatever is after /events as a child page of /events.

Now we just need to register country as a valid query parameter:

function wpse_283774_query_vars( $vars ) {
    $vars[] = 'country';

    return $vars;
}
add_filter( 'query_vars', 'wpse_283774_query_vars' );

Now in your template/functions you can get whatever comes after /events with get_query_var( 'country' ):

if ( get_query_var( 'country' ) ) {
    echo 'Events for ' . get_query_var( 'country' );
}

Just make sure to re-save your Permalinks settings after adding the code.