Questions[gufw](ubuntu)

I have installed ufw and gufw in Ubuntu 18.04 with XFce4.12 environment. I was exploring its configurations, then I looked for some tutorials to configure it and when I run sudo ufw it returns this to me:

ERROR: not enough args

Then I run:

$ sudo ufw enable
Traceback (most recent call last):
  File "/usr/sbin/ufw", line 115, in <module>
    datadir=datadir)
  File "/usr/lib/python3/dist-packages/ufw/frontend.py", line 165, in __init__
    datadir=datadir)
  File "/usr/lib/python3/dist-packages/ufw/backend_iptables.py", line 51, in __init__
    rootdir=rootdir, datadir=datadir)
  File "/usr/lib/python3/dist-packages/ufw/backend.py", line 54, in __init__
    self._get_defaults()
  File "/usr/lib/python3/dist-packages/ufw/backend.py", line 288, in _get_defaults
    for line in orig:
  File "/usr/lib/python3.6/codecs.py", line 321, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xac in position 4: invalid start byte

I can no longer start it, I have uninstalled and reinstalled it and it remains the same, any help please?

I enabled gufw with it's default settings, deny incoming, allow outgoing. I haven't noticed any problems with usability, but I was told that I have to allow incoming UDP traffic from port 68. Do I really need DHCP as a normal user? And if so, do I have to allow incoming traffic from port 68 for proper functionality? What would happen if I didn't?

Finally, if I do have to allow incoming UDP traffic from port 68, would I be able to specify it to only allow traffic from say 192.168.1.1? Or would that still effect the functionality?

I don't know how can I allow the permission for Firefox in the gufw firewall.

Can someone help me please?

I have been told that Ubuntu comes with the firewall UFW. Is this true? Is there a GUI for it? If so, what is its name and where do I download?

Is it possible for UFW to notify us (like in windows with a pop-up window) when someone wants to access to your PC or when an application wants to access the internet?

If not, is there any firewall for Ubuntu that provides such notifications?

I have to open up a group of ports.

Adding the single ports to (g)ufw was easy enough but I can't work out how to open the range 11200-11299.

How do I do that?