How do I add Operations to my custom module's list?

Hi, I’m completely new to Drupal and are still a little bit of a noob when it comes to OOP.

In general what I want to have is a new link in the admin toolbar. When I click on it, a form should open with just a text field and a save/add button. When I enter a text and hit save, the text should be saved in a custom database table.
-> That all I already achieved with the help of this article (my custom module is like this one):

But now I’m stuck:
I want to have an edit/delete operations button (this egg-shaped one) in every added list entry so that I can edit or delete the specific text entry in the database. Now how do I add this?

Do I need some class/function that extends the core’s ConfigEntityListBuilder? And if so, how do I then integrate it to my list in the src/Form/ConfigFormMODULENAME.php?

With the right answer I also hope to learn how to write clean OOP code and how to use these mechanics to develop Drupal 8 modules.
I’m more than thankful for every answer, please help me.
Thank you guys!

Drupal version: