Hi there,
The logo at your logo-bar is actually added by custom css,
.masthead-stacked .x-brand img {
content: url("http://point11.co/wp-content/P11-RE-Logo_main.svg");
width: 100%;
padding-top: 10px;
}
What you need to do is upload your big logo at Admin > Media > Library and get its url. Then simply edit your custom css as above and change its url with the url of your newly uploaded big logo.
Thanks!