Custom CSS messing up all other site elements

Hey ya'll, I made some light custom CSS to achieve this changing text animation (see attached screenshots). But it seems to have overridden other codes as the changing text animation has been appearing on the homepage, in navigations, and in the settings as well (so weird!). Does anyone know what part of the code can be edited to fix this issue?

Thanks for your time and help in advance! 

Best,

Jackie

Code text box:

<div class=“wrapper”>

  <h3><span></span></h3>

</div>

Custom CSS editor:

.wrapper{
  position: absolute;
}
span:before{
  content: ''; 
  animation: animate infinite 10s;
}
@keyframes animate{
  0%{
    content: 'Hi 👋🏽';
  }
  20%{
    content: '你好';
  }
  40%{
    content: 'Hola';
  }
  60%{
    content: 'Ciao';
  }
  80%{
    content: 'Hej';
  }
  100%{
    content: 'Hi 👋🏽';
  }
}

First, edit first code to this

<div class="tuan">
  <h3><span></span></h3>
</div>

Next, edit to this

.tuan {
  position: absolute;
}
.tuan span:before {
  content: ''; 
  animation: animate infinite 10s;
}
@keyframes animate{
  0%{
    content: 'Hi 👋🏽';
  }
  20%{
    content: '你好';
  }
  40%{
    content: 'Hola';
  }
  60%{
    content: 'Ciao';
  }
  80%{
    content: 'Hej';
  }
  100%{
    content: 'Hi 👋🏽';
  }
}