While loops inside an if-statement?

Beginner programmer here:)) I am working on a school project, where the assignment is to find the roots to five functions.

In one of my functions there are two roots, and my code can only find one. Does anyone have any tips or advices? Everything is appreciated!!

PS! (sorry the long code, didn't know what to exclude...) PS!nr.2 (the text and variables are in Norwegian :P)

Just ask if there is something that´s weird;)

def b(x: float):
    return -x**2+x+6

def bgraf():
    xlim(a1, b1)
    ylim(-15, 25)
    x = linspace(-5, 10, 1000)
    y = b(x)
    plot(x, y, 'r')
    return

funksjoner = [0, 1, 2, 3, 4]

while response not in funksjoner:
    i = int(input(" Vennligst velg en av funksjonene, fra 0 til og med 4. \n"))
    response = i
    if response in funksjoner:
        print("Du har valgt graf nr. ", int(funksjoner[i]))

a1 = float(input("1. punkt:  "))
b1 = float(input("2. punkt:  "))
z = a1
y = b1
m = a1
n = b1
NP = True

if int(funksjoner[i]) == funksjoner[1]:
    while abs(y-z) > 1e-10:
        null1 = (z+y)/2
        if b(z)*b(null1)>0 and b(y)*b(null1)>0: 
            NP = False
            print('Det finnes ingen nullpunkt i dette intervallet, se graf.')
            bgraf()
            break
        elif b(null1) == 0:
            break
        elif b(z)*b(null1)>0:
            z = null1
        else :
            y = null1
    while abs(n-m) > 1e-10:
        null1_2 = (m+n)/2
        if b(m)*b(null1_2)>0 and b(n)*b(null1_2)>0: 
            NP = False
            print('Det finnes ingen nullpunkt i dette intervallet, se graf.')
            bgraf()
            break
        elif b(null1_2) == 0:
            break
        elif b(m)*b(null1_2)>0:
            m = null1_2
        else :
            n = null1_2
    if NP :
        print('\n Vi har i dette intervallet et nullpunkt når x =', round(((z+y)/2), 1))
        if null1 != null1_2:
            print('og når x =', round(((m+n)/2), 1))
        bgraf()
        scatter(null1, 0)
        if null1 != null1_2:
            scatter(null1_2, 0)

It looks like python is ignoring the second while-loop I placed under the if-statement. Is there another way I could this?

(The reason I put everything under the while-loop, is because I have all the other graphs in the same file, and do not want to include them, only the one I choose after running the code.)

Thanks for your attention!