Module development and code questions

Hello folks, my first post here in the community.

I have a custom module for my D7 site, what I do in this module is create a entrance in the hook_menu with a item without call back. Them I have others items being a "sub-item" of the first, something like this

I made a module with a form called SimpleForm which consisted of 2 textfields and a submit button. However, I cannot open the form using the path, it always throw HTTP error 500. I also couldn't show the form on my twig file. Can someone please have a look at my code and give me a proper explanation? Thank you beforehand.

honda_model.routing.yml

I've recently run into an issue where after the website was launched. The web address within the iFrame changed in turn dis-configuring the graphics in the content structure. Is there a way to update this without using the hook_update? I'm just learning Drupal out of necessity to update the website.

Thank you in advance!

Hi! I have a site, and when i click on flush cache, the site is loading old css. It creates a new css file, with the old css, and the last file with the latest css version, just lies next to it in the same folder with a different name.

I've problems setting cookies,   cookies are sometimes set and visible in the browser. But not  by code. I'using a form to set. I see a lot answers, but what is the correct way?

use Symfony\Component\HttpFoundation\Cookie;
use Symfony\Component\HttpFoundation\Response;

       This methods, the cookie is set but NOT visible by $_COOKIE

        user_cookie_save([$cookiename => $cookievalue]);

or
       setrawcookie($cookie, $password, time() + (86400 * 30), '/');

good morning

I am making a website in Drupal8 and I need to add an option to run an app that I would have on the phone to make payments online.

They would know how to do that and if they have any docs on it