The first thing to say is that you need to distinguish what you see on screen and what the keyboard layout actually does. Since you have a non-Apple keyboard, you need to look for a keyboard type that is close to what you want. Since there is a key between shift and z, you have an ISO type. Go to the View Menu and choose Keyboard Type. USB Pro might be fairly close to what you have.
Second, it’s a Windows keyboard, so the Windows keys and Alt Gr keys may map to something different. In Ukelele, try pressing them to see what keys are shown as being pressed.
Finally, Apple’s Portuguese keyboard layout seems close to what you want, so I would start from it and make changes (activate it, then create the keyboard layout from the current keyboard input source). The keys to the right of ç seem to be different, and probably some others. Once you work out where you need to make changes, have a look at the tutorials to get an idea of how to make the changes you want.
Keep asking if you get stuck. If you can’t get something to work, let us know what you tried, what happened, and what you expected to happen, and we will have more chance of helping.
John (developer of Ukelele)