React: Web developer tools deforms styling 'CSS'

The styling of my website deforms when I open Web developer tools on Mozilla firefox.

Is there by any chance something I can do to stop it?

Here is an image of the issue:

Code for the header:

.naviga {
  position: fixed;
  top: 0;
  display: flex;
  justify-content: flex-start;
  align-items: center;
  width: 100%;
  height: 13vh;
  background-color: white;
  box-sizing: border-box;
  padding-left: 7vh;
  opacity: 100%;
  border-bottom: 2px solid white;
  position: absolute;
}