First, you'll want to set up paragraph styles for your different levels and create a multilevel list. This is one good resource on how to create the list. https://www.techrepublic.com/article/how-to-link-multilevel-list-levels-to-custom-styles/

One issue with using lists is that they often don't restart at 1 if you have regular text between lists. Here's a workaround: When setting up the list, link the first level to your regular body text style, then delete the numbering for that level.

Link the second level of the list to your first list style. In this one, you can type "Speaker" before the level number. Make sure to check "restart after previous level." This will give you Speaker 1, Speaker 2 etc

Link the third level of the list to the next style. You can now add the number for the previous level. This will give you 1.1, 1.2 etc

Proceed as needed for more levels of lists. By default, Word will also add indents to each level. These can also be changed in your options when setting up the list.