<div id="online">
    <input id="checkButton" type="checkbox">
    <label for="checkButton">
      <div type="button" class="message-bt"></div>
    </label>
    <div class="contact">
      <div class="contactBody">
        <div class="contactBodyMessage">Здравствуйте!</div>
      </div>
      <div class="contactInput">
        <div class="contactInputTextarea">
          <textarea id="textArea" placeholder="Введите ваш вопрос..." rows="1"></textarea>
          <div id="textAreaStatus"></div>
        </div>
        <div class="contactInputButton">
          <button class="contactButtonSend"></button>
        </div>
      </div>
    </div>
  </div>

body {background-color: #eee;}

#online {
  font-family: Arial;
  font-size: 14px;
  line-height: 22px;
  letter-spacing: -.35px;
  text-align: left;
  overflow-wrap: break-word;
  word-break: break-word;
  color: #333;
  box-sizing: border-box; }

.message-bt {
  background: #254bde;
  border: 4px solid #fff;
  border-radius: 50%;
  box-shadow: 0 8px 10px rgba(37,75,222,0.3);
  cursor: pointer;
  height: 58px;
  width: 58px;
  position: fixed;
  right: 3%;
  bottom: 2%;
  z-index: 999;
  transition: .3s; }

.message-bt:hover {
  background-color: #0034ff;
  transition: .3s; }

#checkButton { position: absolute; appearance: none; -webkit-appearance: none; -moz-appearance: none;  }

input#checkButton:checked ~ label .message-bt {
  z-index: 1;
  background-color: #fff;
  transition: .3s;
  box-shadow: 0 0 50px rgba(0,0,0,.4);
  -webkit-animation: none;
  animation: none; }

input#checkButton:checked ~ label .cross {
  position: absolute;
  z-index: 11;
  top: 50%;
  left: 50%;
  transform: translateY(-50%);
  width: 24px;
  height: 24px; }
input#checkButton:checked ~ label .cross::before { background-color: #fff; }
input#checkButton:checked ~ label .cross::before, input#checkButton:checked ~ label .cross::after {
  position: absolute;
  content: '';
  height: 24px;
  width: 3px;
  background-color: #254bde; }
input#checkButton:checked ~ label .cross::before { transform: rotate(45deg); }
input#checkButton:checked ~ label .cross::after { transform: rotate(-45deg); }

.contact { display: none; }

input#checkButton:checked ~ .contact {
  position: absolute;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  z-index: 9999;
  bottom: 100px;
  right: 20px;
  height: 500px;
  width: 400px; }

.contactBody { background-color: #fff; padding: 25px; flex-grow: 1;  flex-shrink: 3; }
.contactBodyMessage { background-color: #f3f4f7; padding: 20px 25px; border-radius: 7px; }
.contactBodyMessage:not(:first-child) { margin-top: 10px; } /* Отступ сверху со второго элемента */




/* Нижняя часть формы */
.contactInput {
  display: flex;
  align-items: flex-end;
  background-color: #fff;
  border-top: 1px solid #ccc;
  border-radius: 0 0 7px 7px;
  padding: 15px 25px; }

.contactInputTextarea { flex-grow: 1; }
.contactInputButton { flex-basis: 40px; padding-left: 20px; }

textarea#textArea {
  font-family: Arial;
  font-size: 14px;
  line-height: 22px;
  letter-spacing: -.35px;
  text-align: left;
  overflow-wrap: break-word;
  word-break: break-word;
  padding: 0 0 10px 0;
  outline: none;
  width: 100%;
  min-height: 12px;
  max-height: 104px;
  border: none;
  resize: none;
  overflow: auto; }

#textAreaStatus {
  position: absolute;
  bottom: 5px;
  left: 25px;
  font-size: 12px;
}

.contactButtonSend {
  position: relative;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid rgba(0,0,0,.3);
  background-color: #254bde; }

.contactButtonSend:hover {
  cursor: pointer;
  background-color: #0034ff; }

.contactButtonSend::before {
  position: absolute;
  top: 10px;
  left: 12px;
  width: 18px;
  height: 18px;
  content: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 15 17'%3E%3Cpath fill='%23ffffff' clip-rule='evenodd' d='M4.483 8.5L1 1l12.632 7.5L1 16l3.483-7.5z'/%3E%3C/svg%3E%0A"); }

function updateSize(e) {
  const target = e.target;
  const clone = e.target.cloneNode(true);
  
  clone.style.position = 'absolute';
  clone.style.left = '-9999px';
  clone.style.height = 'auto';
  clone.style.width = target.scrollWidth + 'px';
  document.body.appendChild(clone);

  const offset = target.offsetHeight - target.clientHeight;
  target.style.height = (clone.scrollHeight + offset) + 'px';

  clone.parentNode.removeChild(clone);
  
  target.scrollTop = target.scrollHeight;
  
  showStatus(target);
}

function showStatus(target) {
  const letters = (target.value.match(/[а-яёА-ЯЁ]/g)||[]).length + 1;
  const status = document.getElementById('textAreaStatus');
  
  if (letters < 50) {
    status.innerHTML = "Вопрос слишком короткий (еще "+ (50-letters) +" букв)";
    status.style.color = "rgb(131,28,28)";
  } else {
    status.innerHTML = "Отличный вопрос";
    status.style.color = "rgb(28,131,40)";
  }
}

document.getElementById('textArea').addEventListener("input", updateSize);