Module development and code questions

Hello,

I have created a customized form with Form API by Drupal 8.

I need to use the data obtained through the form to run a research in the database and print the results with html onto the same page.

I created the form through the buildForm method and I got the data obtained through the form with the submitForm method.

Is there a way to print the results obtained through the form onto the same page through HTML blocks?

I want to override 'preRenderWebformQuizResultSummary' function in custom module to change the result text programmatically.

I need functionality to show different message on particular range of score in Webform Quiz.  I am stuck in override the above function. Please help!
 

I have installed the Time Field For Drupal 8.x / 9.x module to have the start time and end time entered. Works well. I can't calculate the Number of hours. I have $ OraIni and $ OraFin.
   $ OraIni = date ('H: i', $ form ['field_time_mission'] ['widget'] [0] ['from'] ['# value']);
   $ OraFin = date ('H: i', $ form ['field_time_mission'] ['widget'] [0] ['to'] ['# value']);

I'm currently trying to integrate my website into another set of non-PHP back-end code.  I want to use the drupal authentication process, and then trigger certain external activities based on the logged in user.

I had this working under D7 as follows:

1. Get the cookie name - namely, 

strCookieName = "SESS" & Left(sha256(strCookieDomain),32)

2. Read the cookie value

3. Go to the MySQL database, and get the username that cookie belongs to:

Good evening, I'm using drupal 8 and I would like to add the classic Welcome to user in the user menu. in drupal 7 I added a block with php and voila but drupal8 I understand that it does not. My question is is there a module that does it or if there is any way to do it.

slds

My Story:

I'm from Symfony. I have an old symfony4 site. It's an Online Examination Website. I'm maintaining it for years. Now I planned to migrate to Drupal8.

Drupal is amazing and I have developed and hosted two simple sites. It's really great.

Noted: I'm new to Drupal8 and I'm learning it.

Current work: (My work related to this question)