I'm having problems migrating this website to movable type. All is fine, except for this page

I've created a blog called 'Current activities', but don't know how to configure this blog so the structure of this section will be like the site is now. The problem is that it's a mixture of pages and entries. Most of the subsections can be mapped to pages, but suddenly you'll find a 'staff' section within the 'rwanda, drc and burundi' projects which should be entries. The way I think of it now (just applied my theory on the 'rwanda' sections, since the burundi and drc sections are the same structure:

Current activities
Great Lakes Reconciliation Radio a category?
--Background a page?
--Projects a category?
----Rwanda a category?
------Country background a page?
------Strategy a page?
------Programs & activities a category?
--------Soap a page?
--------Factual / debate a page?
--------Grass roots a page?
--------Justice & youth campaigns a page?
------Staff a category with all the staffmembers as entries?
----DRC
------Country background
------Strategy
------Programs & activities
--------Soap
--------Factual / debate
--------Grass roots
--------Justice & youth campaigns
--------Staff
----Burundi
------Country background
------Strategy
------Programs & activities
--------Soap
--------Factual / debate
--------Grass roots
--------Justice & youth campaigns
------Staff
--Evaluation
Sponsors

If it was possible to assign a page to a category the problem wouldn't be so complicated, but I'm struggling to make a simple structure which is understandable for people who are not familiar with mt and can be easily extended with another 'project' of the same structure.

You have the right idea. Just replace categories with folders. Folders are to Pages as Categories are to Entries.

If you want to include entries on a page, try the processtags plugin: http://kalsey.com/2002/08/process_tags_plugin/

Unless you have tonnes of staff, and they're constantly changing, I wouldn't use entries to list them. You can just make a static page for staff, and update as needed.

Here's how I would set it up:

Great Lakes Reconciliation Radio (index page of the current activities folder)
--Background (page in current activities folder)
--Projects (subfolder of current activities folder, and the content goes on the index page of this folder)
----Rwanda (page in projects folder)
----DRC (page in projects folder)
----Burundi (page in projects folder)
--Evaluation (page in current activities folder)
--Sponsors (page in current activities folder)

If you need the information to be deeper, just replace pages with subfolders, and keep going.