This reads like the author has a lisp, with the letter s looking like an f.
In German, we've got words like "dass". Back in the day, every s that wasn't at the end of a word was written as long s, so "dass" would've been written like "daſs", which got turned into ß.
That's why until the recent orthographic reforms of 1996 and 2006 "dass" was written as "daß".
Aside: in some regions, "dass" would've been written like "dasz" / "daſz". That's why the letter is called Eszett (S-Z) even though it's capitalised as two consecutive "s".
I entered school in Germany the very same year that the orthographic reform came into force, so I never learned the legacy spelling, but I certainly found it weird how much adult people at the time detested the rules that six-year-old me considered to be very reasonable (esp. the ss/ß reordering and the ban on fusing tripled consonants in compound words).
This is my very personal perspective. If you're interested in a more complete picture, https://de.wikipedia.org/wiki/Reform_der_deutschen_Rechtschr... looks like a good summary (through translation if necessary).