Your motherboard supports 3200 speed natively, to get anything higher requires over-clocking the BIOS, and this normally just requires XMP mode to be turned on.
Info obtained from here;
Lasting Quality from GIGABYTE.GIGABYTE Ultra Durable™ motherboards bring together a unique blend of features and technologies that offer users the absolute ...
www.gigabyte.com
You'll see the 3400 has O.C. after it, meaning Over Clock.
For me, I'd get the Kingston Fury 3200MHz units, 2x8GB. Or 2x16GB, whatever your budget allows.
That Corsair RM is excellent, see here;
https://cultists.network/140/psu-tier-list/
To double check your memory selection is compatible, download Gigabyte's support list from this page;
https://www.gigabyte.com/Motherboard/B550M-AORUS-ELITE-rev-10-11-12/support#support-doc
As to the CPU cooler, the fan may need replacing, good ones are under $AUD50. Brands like Noctua for example.
Quick fix, spray a bit of WD40, or CRC20, or whatever equivalent oil spray you have over there into the fan bearing.
Sadly, the PSU or RAM may not fix your signal issues, but as said previously, they are the lowest hanging fruit that is worth picking first.
Unless you have access to parts that you can swap in and out, like motherboard, drives, GPU, etc, it's time to either get those new parts we have mentioned or take it to a repair shop, who would have access to spare parts.
And of course, you still have the
"nuke Windows from space" option.
as to "if someone could just answer my previous messages so I can go to the next step", sadly that can't happen as we aren't sitting in front of the unit to see what you are doing.
Try the suggestions, or not - entirely up to you.
But no-one here is going to say "do this and your issue will be fixed"