Why learn integration Suite?
There are going to be a huge requirement for SAP Integration consultants to work on integration project including S/4 HANA and also PI to Integration Suite migration. For the next 5 years there is going to be a huge market.
You can learn SAP Integration Suite by yourself.
Here are some of my best resources for it at the moment:
Trial access
You can get access to a free SAP Integration Suite trial.Takes a few minutes to install but once you have you can use it to learn.
Go to https://www.sap.com/products/technology-platform/pricing.html
Courses
Modernize Integration with SAP Integration Suite
Good overview over the platform.
https://open.sap.com/courses/btp3
Manage B2B Scenarios Effectively with SAP Integration Suite
Going deep into the B2B Add-on. The First module is basic. Module 2+3 lots of content about the B2B Trading Partner Solution
https://open.sap.com/courses/btp4
Most detailed CPI course
Yee Loon Khoo has created a in depth course about how to use SAP Integration Suite.
https://sapintegrationsuitecourse.teachable.com
Free getting started course
My own course on free Cloud Integration. However, it is a few years old.
Learning.sap.com
New courses for Integration Suite
https://learning.sap.com/search?access=free&query=integration+suite&page=1
Faster development with Figaf
One area that you can set yourself a part on is by being able to use Figaf. It is a tool that simplifies how you are developing.
https://figaf.com/figaf-in-your-migration-project/
Migration
It Is probably the number one tool that you need to understand.
Figaf is the ideal tool for the migration.
It is a bit more difficult to get access to a SAP PI/PO system to explore on.