My BackSpace button and Operation buttons are not in harmony and are interrupting 2 different functions

Question

I am making a calcutor app, I will provide the code below: Here is the problem, when i am performing an addition calculation, lets say (3+3+4 = 10) now when i press the backspace key, it works fine and it gets reset to (6 +) and then i can write another number, lets say (5), so it becomes (6 + 5) now and the answer is (11).

However, when after pressing (=), eg- (3+3+4 = 10), if i press (+) once again, instead of making the answer go (10 +), it goes (16 +).

I think it happens because when pressing (+) again, it thinks the 'operationPerformed' is still (+).

In order to tackle that, I added a new line which resets the 'operationPerfomed' after a calculation, this fixes the latter problem but fucks up the prior one and now I cannot perform backspace after hitting (=) :(

Can somebody help me with this, I cannot figure it out cuz I am very new to this (only been coding for 4 weeks, followed a tutorial for this app)

Here is the code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Calculator_App_2
{
    public partial class Form1 : Form
    {
        double initialValue = 0;
        string operationPerformed = "";
        bool isoperationperformed = false;

    public Form1()
    {
        InitializeComponent();
        AnswerBox.Enabled = false;
    }

    private void btnCharacter_click(object sender, EventArgs e)
    {
        AnswerBox.Enabled = true;

        if(AnswerBox.Text == "0")
        {
            AnswerBox.Clear();
        }
        else
        {
            // Do Nothing.
        }

        Button button = (Button)sender;

        if(button.Text == ".")
        {
            if(AnswerBox.Text.Contains("."))
            {
                // Do Nothing.
            }
            else
            {
                AnswerBox.Text = AnswerBox.Text + button.Text;
            }
        }
        else
        {
            AnswerBox.Text = AnswerBox.Text + button.Text;
        }
    }

    private void btnIDK_Click(object sender, EventArgs e)
    {
        AnswerBox.Clear();
        AnswerBox.Text = "Even IDK what's happening ";
        lblPreview.Text = "             LOL BRUH";
    }

    private void btnOperation_click(object sender, EventArgs e)
    {
        if (initialValue != 0)
        {
            btnEquals.PerformClick();
        }

        Button button = (Button)sender;

        operationPerformed = button.Text;
        
        initialValue = double.Parse(AnswerBox.Text);
        lblPreview.Text = initialValue.ToString() + " " + operationPerformed;
        AnswerBox.Clear();
    }

    private void btnEquals_Click(object sender, EventArgs e)
    {
        if(operationPerformed == "+")
        {
            isoperationperformed = true;
            lblPreview.Text = lblPreview.Text + " " + double.Parse(AnswerBox.Text).ToString();
            AnswerBox.Text = (initialValue + double.Parse(AnswerBox.Text)).ToString();
            operationPerformed = "";
        }
        else if(operationPerformed == "-")
        {
            isoperationperformed = true;
            lblPreview.Text = lblPreview.Text + " " + double.Parse(AnswerBox.Text).ToString();
            AnswerBox.Text = (initialValue - double.Parse(AnswerBox.Text)).ToString();
            operationPerformed = "";
        }
        else if (operationPerformed == "×")
        {
            isoperationperformed = true;
            lblPreview.Text = lblPreview.Text + " " + double.Parse(AnswerBox.Text).ToString();
            AnswerBox.Text = (initialValue * double.Parse(AnswerBox.Text)).ToString();
            operationPerformed = "";
        }
        else if (operationPerformed == "÷")
        {
            isoperationperformed = true;
            lblPreview.Text = lblPreview.Text + " " +double.Parse(AnswerBox.Text).ToString();
            AnswerBox.Text = (initialValue / double.Parse(AnswerBox.Text)).ToString();
            operationPerformed = "";
        }
        else if (operationPerformed == "%")
        {
            isoperationperformed = true;
            lblPreview.Text = lblPreview.Text + " " + double.Parse(AnswerBox.Text).ToString();
            AnswerBox.Text = ((initialValue / 100) * double.Parse(AnswerBox.Text)).ToString();
            operationPerformed = "";
        }
    }

    private void btnAC_Click(object sender, EventArgs e)
    {
        AnswerBox.Clear();
        AnswerBox.Text = "0";
        initialValue = 0;
        lblPreview.Text = "Calculator";
        AnswerBox.Enabled = false;
    }

    private void btnBackspace_Click(object sender, EventArgs e)
    {

        if (isoperationperformed == true && AnswerBox.Text.Length > 0)
        {
            lblPreview.Text = initialValue.ToString() + " " + operationPerformed;
            AnswerBox.Text = double.Parse(AnswerBox.Text).ToString();
            AnswerBox.Text = AnswerBox.Text.Remove(AnswerBox.Text.Length - 1);
        }
        else if(AnswerBox.Text.Length > 0)
        {
            AnswerBox.Text = AnswerBox.Text.Remove(AnswerBox.Text.Length - 1);
        }

    }
}
}