I'm not sure about the nuances in Spanish, but in Portuguese (which is very close to Spanish), we use "penúltimo(a)" in the sense "the second to last".
e.g."Ele foi o penúltimo a cruzar a linha de chegada" (He was the second to last in crossing the Finish line).
For "the week before last" I would say "semana retrasada". "Semana atrasada" in Spanish.
I too have a terrible time hearing the difference in a number of sounds, n and m, e and a for starters. Don't get me started on the Swedish vowels that sound different in different words. Does "she" really sound the way Swedes speak? If so I won't understand much of anything there...
The "exercise" pronunciation is quite different to the "discussion" pronunciation; the latter having the same sound for both "ö"s. Frustrating sometimes isn't it! If you listen to the better reproduction in Forvo you get "what I assume is" the correct sound - https://forvo.com/word/f%C3%B6rrf%C3%B6rra/#sv
Good to know Swedish has a simple way for saying a couple time periods before and after the one we're in right now. It seems so cumbersome to me in English to say "the day after the day after tomorrow" when I can easily say "aizparīt" in Latvian, as well as many other simpler ways to express periods that are farther away. Although "the week before last week" doesn't get much simpler with "aizpagājusī nedēļa" :D