Problem with "jumping" main menu

Hi,
I added the followining code to get the custom standard font and bold version on hover/active.
All good so far EXCEPT that the menu items seem to “jump” when you hover over them meaning that they are not static. The bold font on hover seems not to work in this way? Maybe it would be a solution to define absolute positions for the menu items?
What can I do?

Thanks
Carolin

#top #header .avia-menu-text {
font-family: Gilroy-Regular;
font-size:20px;
letter-spacing: 2px;
font-weight: normal;
font-style: normal;
text-decoration: none;
}

#top #header #avia-menu li.menu-item:hover > a > .avia-menu-text {
font-family: Gilroy-Bold;
font-size: 20px;
letter-spacing: 2px;
font-weight: normal;
font-style: normal;
text-decoration: none;
}