Can’t move button with CSS

I have wanted to make a button that is aligned horizontally underneath the text that says “Bubbles”. I have tried flex already and in the snippet I try it with transform but regardless of what I try I wont get the desired outcome. So please Help!

Whole code

section {
  width: 100%;
  height: 100vh;
  overflow: hidden;
  background: #1F69FA;
  display: flex;
  justify-content: center;
  align-items: center;
}

section container {
  height: 200px;
  position: relative;
  border: 3px solid green;
}

section center {
  margin: 0;
  position: absolute;
  top: 50%;
  left: 50%;
  -ms-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}

<section>
  <div class="container">
    <div class="container">
      <button type="button" onclick="next()"> Next </button>
    </div>
  </div>
</section>

Answer

Since you’ve got the container class but aren’t actually using it, we can just make it a flex column and put both elements inside of it

function Seifenblasen_blasen() {
  const section = document.querySelector('section')
  const createElement = document.createElement('spawn')
  var size = Math.random() * 60;
  createElement.style.width = 30 + size + 'px';
  createElement.style.height = 30 + size + 'px';
  createElement.style.left = Math.random() * innerWidth + "px";
  section.appendChild(createElement);

  setTimeout(() => {
    createElement.remove()
  }, 8000)

}
const Blaseninterval = setInterval(Seifenblasen_blasen, 100)

  {
  margin: 0;
  padding: 0;
}

.container {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

section {
  width: 100%;
  height: 100vh;
  overflow: hidden;
  background: #1F69FA;
  display: flex;
  justify-content: center;
  align-items: center;
}

section h2 {
  font-size: 10em;
  color: #333;
  margin: 0 auto;
  text-align: center;
  font-family: consolas;
}

section spawn {
  position: absolute;
  bottom: -80px;
  background: transparent;
  border-radius: 50%;
  pointer-events: none;
  box-shadow: inset 0 0 10px rgba(255, 255, 255, 0.5);
  animation: animate 4s linear infinite;
}

section spawn:before {
  content: '';
  position: absolute;
  width: 100%;
  height: 100%;
  transform: scale(0.25) translate(-70%, -70%);
  background: radial-gradient(#fff, transparent);
  opacity: 0.6;
  border-radius: 50%;
}

@keyframes animate {
  0% {
    transform: translateY(0%);
    opacity: 1;
  }
  99% {
    opacity: 1;
  }
  100% {
    transform: translateY(-2000%);
    opacity: 0;
  }
  section span {
    margin-top: 700px;
    font-size: 1em;
    color: #333;
    margin: 0 auto;
    font-family: consolas;
    background-color: #1F69FA;
    border: none;
    position: absolute;
  }
  section container {
    height: 200px;
    position: relative;
    border: 3px solid green;
  }
  section center {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
  }

<section>
  <div class="container">
    <h2> Bubbles </h2>
    <button type="button" onclick="next()"> Next </button>
  </div>
</section>