Hi AnnaLisa,
Thank you so much for using our theme AcmeBlog. In the case of logo, if you want to add the logo size bigger and write your own css, it may work for you but sometimes it may arise issues on responsive view. So before adding any line of code, make sure it may work properly or may arise some issues too.
On the case of logo size, would you please provide the link of your site so that it help us for debugging your problem more easier.
Note: Child theme is recommended to customize theme.
Thanks you
Acme Supports