How to break a program into components?

Question

Java

There is a big project that I started writing over a year ago when I wanted to learn how to work with spring.
This project is a big dump where everything is mixed into one heap. Now I wanted to break everything into components, into jars, and a few questions appeared:
1) I make jars into which I take out all the auxiliary classes that are not connected in any way, but the fact that they are not connected to each other unites them, so I want them put in one package. All these classes are very large and I don’t really want to create one project for all of them at once.
I want to create a project for each class separately, collect jars, and then cram all such jars into one package. And then, using this package somewhere, I could access any jar from this package. Over time, this package will be replenished with new jars. And I want to add a jar to the package in two clicks, and not download the code with all the classes, get into the package, create a new class there, then recompile the whole thing, as it would be if I collected all these classes in one project.
2) Here I have a lot of my libraries that I use in the project. Can I somehow get the original code of the library, put a bug there, debug it? If you click on the variable type in idea, then if this type is from the library, then idea will decompile the jar and show the decompiled file, which is less readable compared to the original)
Of course, I have the original code, I understand that the compiler compiles from the jar and how he will compile it, no one knows) The question is to say idea, ml do not decompile this jar, but look at the original code)

Answer 1

1) write build targets and projects in maven \ gradle
2) this is in idea, you just need to poke your nose where the source code is.