if i have the transfer function of magnitude response is there a method that i could calculate the frequency response?
For example the transfer function of the magnitude response is:
$ 3db \pm 3.5db $ for $|ν|<0.1$
$ <-55db $ for $|ν|<0.2$
The frequency response of a system can be represented in polar format, in which the magnitude and phase response are considered separately:
$$ H(\omega) = |H(\omega)| \angle H(\omega) $$
With this representation, it should be clear that the magnitude response alone is not sufficient to characterize the full frequency response of a system; you have to know (or assume) what its phase response is also.