Welcome to the forum Dida.
You can import documents into other documents by using the "Page -> Import" function. However, if you have a lot of images in your chapters, you might come up against system memory issues (unless your machine can handle it, all you can do is try it and see what happens).
If you want to keep your chapters separate you can change the page numbers for each chapter by going to "File -> Document Setup" then go to the "Sections" section. Then change the "Start" value to the page number you want that chapter to start at. Obviously you'll need to do this in ascending chapter order so you know which page number to give each one. (After applying the change you may need to close then re-open the document to see it.)
To get Scribus to do a Table of Contents for the whole book you will need to have the whole book in the same document. Scribus can't - yet - handle a TOC across multiple documents. This page will show you how to create a TOC:
https://wiki.scribus.net/canvas/Creating_a_Table_of_Contents (It's a little complicated at first but it works. Unfortunately there's not much you can change formatting-wise so sometimes it's best to do the TOC manually.)
I hope this has been helpful in some way.