Please follow this codex link https://codex.www.ads-software.com/I18n_for_WordPress_Developers

All the strings should be in translation functions, then you can use any plugin for the transalation.

Thanks

add_filter( 'gettext', 'ps_change_login_string', 20, 3 );
function ps_change_login_string( $translated_text, $text, $domain ) {

        switch ( $translated_text ) {

            case 'your string here' :

                $translated_text = __( 'translated string', 'theme_text_domain' );
                break;

        }

    return $translated_text;
}

Replace the string with your text.

Here’s the code I added in my functions.php:

add_filter( ‘gettext’, ‘ps_change_login_string’, 20, 3 );
function ps_change_login_string( $translated_text, $text, $domain ) {

switch ( $translated_text ) {

case ‘Client Login’ :

$translated_text = __( ‘Client Login’, ‘theme_text_domain’ );
break;

}

return $translated_text;
}

Did I correctly replace the string?

$translated_text = __( ‘Client Login’, ‘theme_text_domain’ );

Here you need to paste the string that you want to show that means translated string.

add_filter( ‘gettext’, ‘ps_change_login_string’, 20, 3 );
function ps_change_login_string( $translated_text, $text, $domain ) {

switch ( $translated_text ) {

case ‘Ingreso Cliente’ :

$translated_text = __( ‘Client Login’, ‘theme_text_domain’ );
break;

}

return $translated_text;
}

<div class=”botonclientes”>
<button type=”button” class=”clientes”> <span class=”dashicons dashicons-arrow-right-alt2″></span><?php _e(‘Ingreso Cliente’, ‘text-domain’);?>
</button>
</div>