So now it seems correct but I don't know if this is the proper solution or if it could be a better one?
Hi @takis.
This decision is not correct.
.logo-image {
max-width: none;
}
And this is also not correct img { width: auto; height: auto; object-fit: cover; }.
Using img as a selector, you apply this code to all images on the site. Because of this, the problem with the logo arose.
Remove all this.
Correct solution:
Add your own class to the Gallery Addon settings (Style Tab > scroll down > CSS Class field).

And use it for accurate aiming to the elements you need.
For example, if you add this class name my-gallery, then the code will be like that.
.my-gallery .sppb-img-responsive {
object-fit: cover;
}
And that's all that is required. No need width: auto; height: auto;, moreover, auto values do not work with object-fit: cover; . So, this is just an useless trash. You set up image width and height in the Addon settings.
Then you can simply add this class to other galleries. Write the code is not required again.