I extracted the files using win.rar and I found some interesting things. I found a file called decterm.ttf I open this file and saw something weird. I see the words "The quick brown fox jumps over the lazy dog. 1234567890". The quotes weren't there tho. These words progressively get larger on the file. There are multiple other files but it is a bunch of code and the letter ÿ repeated thousands of times. I have no clue if any of this is important but it could be a step in sloving this mystery
Thats normal for a windows font file, it has that for every font.
The ÿ thing is just you are opening a data file as a txt file, it isnt being read right.
Try opening solution.png as a hex or text file though, it says "Do you understand me? Nobody does. The truth is deeper inside. - 467767 - Listen again. - 467767 - Listen again. - 467767 - Listen again. - 467767 - Listen again. - 467767 - Listen again. - 467767 - Listen again."