Definitions of fix
to agree on a price, details of a contract, time, place etc
Fixed rates carry early repayment charges though so my advice would be not to fix for longer than you feel you are likely to stay in your current property.
to repair
The recent technical problems have been fixed.
to represent something in a concrete form such as print, sound recording, film, etc.
The politician's speech was not eligible for copyright protection because it was not fixed in speech or writing.