… and this is what I see in Brave (Chromium) and Windows 10.
I have no idea what you mean by a “Parallax Image”: you want to use an image format (webp, jpeg, png, gif) which works for most browsers.
As the images in your portfolio section are all .webp files, you may be facing a limitation of your browser of choice. When authoring web pages, it’s always wise to try to use features that will work in the browser(s) you want to support. See, for instance, https://caniuse.com/ for information on what CSS, HTML, etc are supported in specific browsers or versions.
Another piece of free advice: make your page smaller. Your header image is pretty large - try it on a mobile device (e.g. iphone, android phone/tablet) and see how it looks.