There are five main areas in Affinity Designer.
We have our main document workspace in the centre.
All of our tools are on the left side.
We have studio panels on the right side.
We have a toolbar at the very top.
Underside that, we have a context toolbar. Each tool comes with different settings that you can modify.
Hint:
If you lose a toolbar, you may have it hidden, so go to View and deselect the Hide Toolbar.
If you lose the Studio, this can be reset in the Windows menu at the top