How do i for use the function "OR"? --- there is no function or, use if

Surely not ;-)

There is no "function" or.
or is an operator to build conditionals to be used in if/while constructs.

Supposing CapturaTela() is a private function, that should be called, if the image "Faturamentcd.png" does not appear within 30 seconds:

if not exists("Faturamentcd.png", 30):
    CapturaTela() # repair the problem
# here the normal workflow continues

Come back with more info on what you want to achieve, if I did not guess right.

BTW: Sikuli talks Python language level 2.5 (Interpreter used internally is Jython 2.5)