Hi Yande 

There are two articles that may be helpful in explaining how the example Self Service pages can be edited.

(+) Sage CRM 2019 R1: Understanding the code in the Self Service Demo (Part 1 of 2) - Sage CRM Hints, Tips and Tricks - Sage CRM - Sage City Community

(+) Sage CRM 2019 R1: Understanding the code in the Self Service Demo (Part 2 of 2) - Sage CRM Hints, Tips and Tricks - Sage CRM - Sage City Community

Self Service is an API and can be used as you want.

As for adding a page to use for Web to Lead, the functionality for Web to Lead is much simpler than Self Service - essentially you can just create a static HTML page that contains the form for Web to Lead.

Hi Yande 

There are two articles that may be helpful in explaining how the example Self Service pages can be edited.

(+) Sage CRM 2019 R1: Understanding the code in the Self Service Demo (Part 1 of 2) - Sage CRM Hints, Tips and Tricks - Sage CRM - Sage City Community

(+) Sage CRM 2019 R1: Understanding the code in the Self Service Demo (Part 2 of 2) - Sage CRM Hints, Tips and Tricks - Sage CRM - Sage City Community

Self Service is an API and can be used as you want.

As for adding a page to use for Web to Lead, the functionality for Web to Lead is much simpler than Self Service - essentially you can just create a static HTML page that contains the form for Web to Lead.