I am still struggling with this challenge

if you write a solution in python, you should consider slice instead of using s[-1].
However, it is just a temprary solution to avoid that error, so let me know if you got a better solution.

I am getting "IndexError: string index out of range" error

I am stuck here: 'First a of in' should equal 'First A Of In'

Please mark your post as having spoiler content next time.

See the example in the description, the input is not in the error message, the first value is your wrong answer, the one with less spaces in it and the second one is the expected answer, with double spaces.
This is the test:

#                                     input value          expected reversed value
test.assert_equals(reverse_words('double  spaced  words'), 'elbuod  decaps  sdrow')

I am sorry but the text is not being reversed; what i can see is only the addition of a space between the words

'elbuod decaps sdrow' = > 'elbuod decaps sdrow' (only the spaces added here)

look at the length and the individual bytes of your string - it does not work perfectly, you are not measuring correctly. granted, I can see how that would be confusing, but, it also seems like the sort of thing to watch out for in C with all the footguns available

The error message is:

'elbuod decaps sdrow'     should equal 
'elbuod  decaps  sdrow'

Your solution does not preserve adjacent spaces.

I need your help guys.

My code passes three tests until I get to the bellow

Expected: 'elbuod decaps sdrow' should equal 'elbuod decaps sdrow'

For the 4th test, my function returns "double spaced words"
If I split the above text into a list then reverse word by word then I will get the following:
elbuod = > double
decaps = > spaced
sdrow = > words

Therefore I expected the final text to be
elbuod decaps sdrow = > double spaced words

I don't understand what is required here