Hello @robinpettersson,
Regarding the speed optimizations, please follow the steps explained following:
GTmetrix Grade:
First, I should know where is the website server! So I always recommended the users using the CDN so that issue is fixed automatically! Mostly more than 60% in performance.
Page Details:
It shouldn’t have many heavy files, so sometimes “1.35MB” may is a large number, like this one: https://i.postimg.cc/YqfBxX9P/image.png.
I’ll suggest reducing file sizes!
Minifying Assets:
To reducing all assets file on websites, using minified tools, combine tools and cache plugins do all of them in one package. They should upload all images lighter.
Server Optimization:
TTFB; This is related to the host configurations, and users should use the compatible host with WordPress. (LINK).
Then above steps: You have to solve a series of problems that, for example, GTMetrix suggests.
PageSpeed tab:
The PageSpeed tab is the default active tab when you run a GTmetrix test. It grades your website against Google’s PageSpeed rules.
Performance tab:
Here you can find the problems caused by each loaded asset on your site with its description.
The Waterfall tab:
is a bit advanced, but it’s a handy tool to understand how the different parts of your site load and where there might be small bottlenecks that slow down your entire site.
I found another link for you that has useful content that can help you in this regard:
https://www.codeinwp.com/blog/gtmetrix-speed-test-tutorial/
https://gtmetrix.com/wordpress-optimization-guide.html
And in the end, please don’t forget to read this article: https://webnus.net/dox/modern-events-calendar/assets-per-page/.
+ find our speed optimization articles here: https://webnus.net/?s=speed
Best Regards