A “factory seconds” framework 13 might fit your budget, and you get a laptop that is easily repairable and upgradeable. The 11th gen i7 version that starts at $500 is what I have been using for a couple of years now and still runs great.
They also have refurbished laptops, but those seem to start a little bit more expensive.
From the btrfs page on the archwiki
General linux userspace tools such as df(1) will inaccurately report free space on a Btrfs partition. It is recommended to use
btrfs filesystem usageto query Btrfs partitions.
You don’t even need any hardware to get started. Fire up a virtual machine in VirtualBox or VMWare or use WSL. Start playing around, find a distro/DE you like and start learning.
After some time, look into dual booting your existing machine. You can try this in a virtual machine first before making any changes to you hardware.
I ran Lineage on my OnePlus 5 for a few years until I replaced it with a Pixel 8 last month. The first thing I did with it was install GrapheneOS. I have not had any issues so far.
Cyanogenmod became LineageOS. It can be run fully de-googled or with Gapps.
GrapheneOS is also worth looking at.
Both run on modern hardware and are super simple to install.
Do you have an earlier snapshot that you can roll back to? If not then this is a learning experience about how you should take a snapshot before doing any configuration changes/updates. And also maybe some automatic ones on a schedule (daily/weekly).
As far as recovering files, you could try the Windows recovery environment (or whatever they call it). Take a snapshot first, in case it makes things worse.
You could also try mounting the virtual disk to your host system. https://www.baeldung.com/linux/mount-qcow2-image
Or try booting the VM with a live boot environment of your favorite distro, similar to how you would do recovery from a dead physical machine.
Firefox