how to plot on the same bode plot a manual function plot() with function bode()?
This is just a concept, but you could transform f2 to be a transfer function, e.g. tf2 = xx2tf(f2) (if it's not already, since it seems you are already talking about f2(s)), and then just run:

[F2mag, F2phi, w] = bode(tf2);


and then use mag, together with hold on/off and plot:

plot(w, abs(f1)), "", w, F2mag);


Or the reverse, transform f1 to tf() and then do as in the comment:

bode(...);
hold on;
bode(...);
hold off;