Responsive Design not working

Hello,

I tried some… adding for example this to the additional CSS:

@media only screen and (max-width: 768px) {
#header {
background-attachment: initial !important;
}
#header .bottom-header h2 {
font-size:66px;
}
}
#page #logo img {
max-width: 100%;
}
/* #site-title a img {
vertical-align: inherit;
max-width: 96%;
}

`
But now I think everything shuold be like in the beginning.

Something else I did - I installed the parallax-plugin for having the title removed and placed an image instead. I suppose this image (the red letters in the middle) causes the problem…
(https://colorlibsupport.com/t/changing-header-titel-to-image-on-static-page-and-changing-font/)

Thanks for your help!
Liilou