Calling a function within a function does not work properly

I am trying to open a function out of another function. When i run both functions seperately, they work pefectly fine. As soon as I try to open one of the functions out of the other one it gives me the following error:

_tkinter.TclError: image "pyimage5" doesn't exist

These are the two functions:

def ah():
    root=Tk()
    root.geometry('400x400')
    root.title('Results')
    root.minsize(400,400)
    root.maxsize(400,400)

    bg= PhotoImage(file='D:/Informatica eindopdracht/achtergrond.png')
    label=Label(root, image=bg)
    label.place(x=0, y=0, relwidth=1, relheight=1)

    close= Button(uitslag, text='Afsluiten', bd='5', height='2', width='15', command=root.destroy())
    close.place(x=0, y=353)

    mainloop()

def nextwin():
    global volgendeR
    
    def count():
        menu.counter += 1
        
    count()
        
    if menu.counter == rounds:
        nextwin.destroy()
    else:
        result=Button(spelmenu, text="Next round", bd='5', height='2', width='15', command=spelmenu()
        result.place(x=150, y=350)

The nextwin() function is called into a window that already exists. Therefore this function does not have a root=Tk(). The spelmenu window mentioned in the result button is a different window which contains the rest of the game. Same goes for the function that is linked to the command. This is not an issue at all.

I use the following function to get the amount of rounds via user input:

def nameANDround():
    global rondes

    w = Tk()
    w.geometry('600x600')
    w.title('Pick a name')
    w.minsize(400, 400)
    w.maxsize(400, 400)

    naam1Label=Label(w, text="Player 1")
    naam2Label=Label(w, text="Player 2")
    naam3Label=Label(w, text="Player 3")
    rondesLabel=Label(w, text="Rounds")
    
    naam1Label.place(x=100, y=120)
    naam2Label.place(x=100, y=140)
    naam3Label.place(x=100, y=160)
    rondesLabel.place(x=67, y=178)

    Naam1=Entry(w)
    Naam2=Entry(w)
    Naam3=Entry(w)
    rounds=Entry(w)
    
    Naam1.place(x=145, y=120)
    Naam2.place(x=145, y=140)
    Naam3.place(x=145, y=160)
    rounds.place(x=145, y=180)

    save=Button(w, height=1, width=10, text='Opslaan', command=nummer)
    save.place(relx=0.5, rely=0.72, anchor=CENTER)

    Naam1_var=StringVar()
    Naam2_var=StringVar()
    Naam3_var=StringVar()
    
    mainloop()

The command linked to the save button is a function that checks if the round input is an integer. The two questions that remain are these:

1. How do I open the ah() function out of the nextwin() function without it giving me an error.

2. How do I make it so the if...else function properly works within the nextwin() function. It is currently either ignoring the if or the else function

Edit: The first question has been resolved