header {
background-color: #0069ed;
position: fixed;
top: 0;
left: 0;
right: 0;
height: 50px;
display: flex;
flex-direction: row;
align-items: center;
z-index: 9;
box-shadow: 0 0 25px 0 black;
color: white;
}

header > .back:nth-child(2) {
    order: 1;
    position: fixed;
    left: 15px;
}

header :nth-child(1) {
    order: 2;
}

header > .next:nth-child(3) {
    order: 3;
    position: fixed;
    right: 15px;
}

.title{
text-align: center;
right: 0;
left: 0;
position: fixed;
}

.next {
  width: 0;
  height: 0;
  border: 10px solid transparent;
  border-right: 0;
  border-left: 15px solid white;
  position: fixed;
  right: 15px;
  display: none;
}

.back {
  width: 0;
  height: 0;
  border: 10px solid transparent;
  border-left: 0;
  border-right: 15px solid white;
  position: fixed;
  left: 15px;
  display: none;
}