nick_sh

If you mean you don't want header to stay on top scroll, you need to removed Fixed header somewhere in header options

.header-nav-item a span { display: block; }  

Yeah I tried but no luck. Had to recreate the website.

To remove:
@media(min-width: 601px) and (max-width: 1200px) { .fe-block-yui_3_17_2_1_1708083773595_75032 { display: none; } } but maybe use one image as @Snowday suggested

The flex-start code it correct, it works for me with flex-start. But maybe add !important;

There are 3 options:
1. You can try redirecting with js from portfolio page itself, not sure how it's treaded by Google though. Try adding to code block:
<script> window.location.replace('URL') </script> 2. Alternatively, move portfolio page to not linked, and hide it from SEO. 
3. You can add regular sections to portfolio page, so you can just use those and hide the actual portfolio section.

.blog-item-author-profile-wrapper .author-avatar-image { top: 0 !important; left: 0 !important; }  

.header--menu-open .header .header-burger:after { color: ... }  

Apparently I found  a solution long ago, but forgot to post. Single portfolio pages can be targeted via body id that contains item. Code needs to be added in portfolio page settings → advanced → code injection:
[id*="item"] ...YOUR CLASSES HERE... { }  

It's something with how bold font is uploaded, try reuploading it? 

@Katberg try adding this to Code Injection
 
<script> addEventListener("DOMContentLoaded", (event) => { document.querySelectorAll('section[data-section-id="65c38c2f3d8bf72234d2ac79"] a').forEach(link => { link.addEventListener('click', e => { e.preventDefault(); }) }); }); </script>

@mart22 It needs to be Halyard Display book

@media (max-width: 767px) { .checkbox .option { width: 100% !important; } }  

you can try adding to Custom CSS
#header:hover a, #header:hover img, #header:hover svg { filter: invert(1); } It assumes items are black → they will invert to white.  Not sure if it covers all elements though. 

.gallery-masonry-item-wrapper::after, figcaption.gallery-caption { pointer-events: none !important; }

Re:body — I forgot to mention: you need to view with full screen editor (so no admin sidebar is visible → click on arrow in right top corner to expand) or incognito.
This will do nothing because you need fluid engine class in your case. Because you make regular block unclickable, but fluid engine block remains. 
Try this code to see that actual :
.fe-block-yui_3_17_2_1_1707856363106_10388 { pointer-events: none; border: 1px solid red; }  
Here you need  dot before the class:
.fe-block{ border: 5px solid red; }

You need to open .svg file in any text editor, copy the code and insert into Code Block

Add this to website → website tools → custom CSS:
.ProductItem-gallery-slides-item img { object-fit: contain !important; }  

Opaque correct selector seems to be: 
.sqs-video-wrapper .sqs-video-overlay .sqs-video-opaque  
Title: 
.image-slide-title { ...your styles... overflow: visible !important; margin-top: 0 !important; }  

Got it, if you feel headings are small, you can set font sizes manually (add to Custom CSS):
@media screen and (min-width: 1920px) .html-block h1 { font-size: ~"calc(var(--heading-1-size-value) * 1rem)" !important; } } You can play with 1 rem there. E.g.:
@media screen and (min-width: 1920px) .html-block h1 { font-size: ~"calc(var(--heading-1-size-value) * 1.4rem)" !important; } } Or just 
@media screen and (min-width: 1920px) .html-block h1 { font-size: 90px !important; } }  

Basic idea would be like this, you can further play with the styles. 
.fe-block-53a098b9fb8dd2261803 { counter-reset: section; } .fe-block-53a098b9fb8dd2261803 .summary-item { display: flex; } .fe-block-53a098b9fb8dd2261803 .summary-item:before { counter-increment: section; content: counter(section) "."; line-height: 1; color: var(--headingLargeColor); font-family: var(--heading-font-font-family); font-style: var(--heading-font-font-style); font-weight: var(--heading-font-font-weight); font-size: 22px; margin-right: 12px; position: relative; top: -4px; }  

You need to target #site-title: 
#site-title { font-family: 'adonis-web' ; }  

It shows the links for me:

.ProductItem-gallery-current-slide-indicator { display: none; } Add to Website > Utilities > Website Tools > Custom CSS

Not sure how you added, but try adding explicitly to and use !important: 
.portfolio-hover-item-content { font-family: YOUR FONT !important; }