Hi Jesus,
Can you link us to the site in question?
Normally, the logo can be adjusted through Appearance > Customize > Site identity.
But if your site has “Use header as navigation” enabled, the option to change the logo width disappears.
In this case, we use custom CSS.
You can try this out:
.navigation-branding img{
height:auto;
width: 100px;
}
Just change the width to the deserved size value.
A wise man once said:
"Have you cleared your cache?"