JSFiddle - React, Tailwind, and code Playground

HTML

<div class="form-step">
      <div class="input-group">
      </div>
      <div class="type-window div-center">
        <label class="radio-container">
          <input type="radio" class="radio-input" id="etplan" name="plan">
          <div class="custom-radio div-center">
            <span class="radio-label">1 plan</span>
          </div>
        </label>
        <label class="radio-container">
          <input type="radio" class="radio-input" id="toplan" name="plan">
          <div class="custom-radio">
            <span class="radio-label">2 plan</span>
          </div>
        </label>
        <label class="radio-container">
          <input type="radio" class="radio-input" id="etagelejlighed" name="plan">
          <div class="custom-radio">
            <span class="radio-label">Etagelejlighed med ståadgang via altan eller svalegang</span>
          </div>
        </label>
      </div>
      <div class="">
        <a href="#" class="btn btn-next width-50 ml-auto">Next</a>
      </div>
    </div>
    <div class="form-step">
      <div class="input-group">
        <div class="grid-container">
                      <div class="grid-item">
              <div class="image-section">
                <img decoding="async" src="https://vinduespudser.dk//wp-content/uploads/2024/01/01vindue1.webp" alt="Vindue 1 rude">
              </div>
              <div class="content-section">
                <div class="window-text">Vindue 1 rude</div>
                <div class="number-input-container">
                  <!-- lejlighed -->
                  <input type="number" class="lejlighed-item" id="lejlighed-item2Count" name="lejlighed-item2Count" min="0" value="0" style="display: none;">
                  <input type="hidden" id="lejlighed-item2Price" name="lejlighed-item2Price" value="127">
                  <!-- 1. sal -->
                  <input type="number" class="sal-item" id="sal-item2Count" name="sal-item2Count" min="0" value="0" style="display:...

CSS

.container {
  max-width: 1000px;
  margin: 20px auto;
  background-color: #ffffff;
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

:root {
  --primary-color: #1a7efb;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

/* Global Stylings */
label {
  display: block;
  margin-bottom: 0.5rem;
}

input {
  width: 100%;
  padding: 0.75rem;
  border: 1px solid #ccc;
  border-radius: 0.25rem;
}

.width-50 {
  width: 50%;
}

.ml-auto {
  margin-left: auto;
}

.text-center {
  text-align: center;
}

.div-center {
  display: grid;
  padding-bottom: 30px;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  justify-items: center;
}

/* Progressbar */
.progressbar {
  position: relative;
  display: flex;
  justify-content: space-between;
  counter-reset: step;
  margin: 0rem 0rem 4rem;
}

.progressbar::before,
.progress {
  content: "";
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  height: 4px;
  width: 100%;
  background-color: #dcdcdc;
}

.progress {
  background-color: var(--primary-color);
  width: 0%;
  transition: 0.3s;
}

.progress-step {
  width: 2.1875rem;
  height: 2.1875rem;
  background-color: #dcdcdc;
  border-radius: 50%;
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1;

}

.progress-step::before {
  counter-increment: step;
  content: counter(step);
}

.progress-step::after {
  content: attr(data-title);
  position: absolute;
  top: calc(100% + 0.5rem);
  font-size: 0.85rem;
  color: #666;
}

.progress-step-active {
  background-color: var(--primary-color);
  color: #f3f3f3;
}

/* Form */
.form {
  margin: 0 auto;
  padding: 1rem;
}

.form-step {
  display: none;

}

.form-step-active {
  display: block;
}

.input-group {
  margin: 2rem 0;
}


/* Button */
.btns-group {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.btn {
  padding: 0.75rem;
  display: block;
  text-decoration: none;
  background-color:...

JavaScript

document.addEventListener('DOMContentLoaded', function () {
  var radioContainers = document.querySelectorAll('.form-step .type-window');
  var numberInputContainers = document.querySelectorAll('.form-step .number-input-container');

  console.log("radioContainers:", radioContainers);


  radioContainers.forEach(function (radioContainer, index) {
    var radioButtons = radioContainer.querySelectorAll('input[name="plan"]');
    var numberInputContainer = numberInputContainers[index];

    radioButtons.forEach(function (radioButton) {
      radioButton.addEventListener('change', function () {
        hideAllNumberInputContainers();

        if (radioButton.id === 'etplan') {
          showNumberInputContainer(numberInputContainer, 'stue-item');
        } else if (radioButton.id === 'toplan') {
          showNumberInputContainer(numberInputContainer, 'stue-item');
          showNumberInputContainer(numberInputContainer, 'sal-item');
        } else if (radioButton.id === 'etagelejlighed') {
          showNumberInputContainer(numberInputContainer, 'lejlighed-item');
        }
      });
    });
  });

  function hideAllNumberInputContainers() {
    numberInputContainers.forEach(function (container) {
      var inputs = container.querySelectorAll('input[type="number"]');
      inputs.forEach(function (input) {
        input.style.display = 'none';
      });
    });
  };

  function showNumberInputContainer(container, selector) {
    var inputs = container.getElementsByClassName(selector);
    Array.from(inputs).forEach(function (input) {
      input.style.display = 'inline-block';
    });
  }
});