Python - My counter doesn't count the time when I press the start button and also doesn't reset

Question

I am trying to make pomodoro software. However, my counter doesn't work at all. I couldn't understand the reason. I hope you can help me to solve this issue. I basically try to count down from 25 minutes with seconds if my mode is working mode. If my work is break mode, I want to count down from 5 minutes. Many thanks in advance.

  # ---------------------------- CONSTANTS ------------------------------- #
    PINK = "#e2979c"
    RED = "#e7305b"
    GREEN = "#9bdeac"
    YELLOW = "#f7f5dd"
    FONT_NAME = "Courier"
    WORK_MIN = 25
    SHORT_BREAK_MIN = 5
    LONG_BREAK_MIN = 20
    
    
    # ---------------------------- TIMER RESET ------------------------------- #
    def reset_time(mode):
        if mode == "working":
            minutes = 25
            seconds = 0
            canvas.itemconfig(time_c, text=f"{minutes}:{seconds}")
        elif mode == "break":
            minutes = 5
            seconds = 0
            canvas.itemconfig(time_c, text=f"{minutes}:{seconds}")
    
    
    # ---------------------------- TIMER MECHANISM ------------------------------- #
    def start_timer(mode,start):
        if mode == "working":
            minutes = 24
            seconds = 59
            if start == 0:
                canvas.itemconfig(time_c, text=f"{minutes}:{seconds}")
                start += 1
        elif mode == "break":
            minutes = 4
            seconds = 59
            if start == 0:
                canvas.itemconfig(time_c, text=f"{minutes}:{seconds}")
                start += 1
        count(mode,minutes,seconds)
     
    
    # ---------------------------- COUNTDOWN MECHANISM ------------------------------- # 
    
    def count(mode, minutes, seconds):
        if mode == "working":
            while seconds <= 60:
                if seconds == 0:
                    if minutes == 0 and seconds == 0:
                        mode = "break"
                        start = 0
                        break
                    seconds = 60
                    minutes -= 1
                seconds -= 1
                canvas.itemconfig(time_c, text=f"{minutes}:{seconds}")
        elif mode == "break":
            while seconds <= 60:
                if seconds == 0:
                    if minutes == 0 and seconds == 0:
                        mode = "working"
                        start = 0
                        break
                    seconds = 60
                    minutes -= 1
                seconds -= 1
                canvas.itemconfig(time_c, text=f"{minutes}:{seconds}")
    
    
    # ---------------------------- UI SETUP ------------------------------- #
    from tkinter import *
    
    mode = "working"
    start = 0
    minutes=25
    seconds=0
    window = Tk()
    window.title("Pomodoro Powered By MFE")
    window.minsize(width=300, height=300)
    window.configure(padx=100, pady=50, bg=YELLOW)
    
    label_timer = Label(text="Timer", fg=GREEN, bg=YELLOW, font=(FONT_NAME, 20, "bold"))
    label_timer.grid(column=2, row=1)
    
    canvas = Canvas(window, width=210, height=223, bg=YELLOW, highlightthickness=0)
    canvas.grid(column=2, row=2)
    img = PhotoImage(file="tomato.png")
    img_sip = canvas.create_image(7, 0, anchor=NW, image=img)
    time_c = canvas.create_text(100, 112, text=f"{minutes},{seconds}", fill="white", font=(FONT_NAME, 30, "bold"))
    
    button_start = Button(text="Start", bg="white", command=start_timer(mode=str(mode),start=start), highlightthickness=0)
    button_start.grid(ipadx=2, ipady=2, column=1, row=3)
    
    button_reset = Button(text="Reset", bg="white", command=reset_time(mode=str(mode)), highlightthickness=0)
    button_reset.grid(ipadx=2, ipady=2, column=3, row=3)
    
    label_tick = Label(text="✔", bg=YELLOW, fg=GREEN, font=(FONT_NAME, 15, "bold"))
    label_tick.grid(column=2, row=3)
    
    window.mainloop()