JSFiddle - React, Tailwind, and code Playground

HTML

<div id="conv">

</div>
<form id="form">
  <label>
    <select>
      <option value="witam" selected>Witam</option> 
      <option value="żegnam">żegnam</option>
      <option value="no elo">no elo</option>
      <option value="rozmawiamy sobie">rozmawiamy sobie</option>
    </select>
  </label>
  <button>
    Ślij
  </button>
</form>

JavaScript

const conv = document.getElementById('conv');
const form = document.getElementById('form');

form.addEventListener('submit', event => {
	event.preventDefault();
	const select = event.target.querySelector('select');
  const p = document.createElement('p');
  p.textContent = `user: ${select.options[select.selectedIndex].value}`;
  
  conv.appendChild(p);
});