How can i insert the right logo size without destroying the header menu?
Why isn’t there just one ideal size?
I guess there’s no ideal size because different templates have different header sizes. And also the logos are different, maybe you have a logo that it’s focused around an icon and you could use a smaller sized logo, but I have a logo with text that I need to be visible and for that I use a larger size.
Coming back to a solution for you, you may try to give the image you want to use a max-width in css in a way to not destroy the header.