I seem to have a problem with internet connectivity. I use NetworkManager with Proton VPN on an Arch KDE system. The wifi and VPN stay connected, but every once in a while the upload and download rates will go down to, at most, a few hundred KiB/s. The issue can be solved temporarily by disconnecting and reconnecting the VPN, but as I’ve had a similar issue without the VPN before, I do not know whether this is a VPN issue or a NetworkManager issue.
You must isolate the problem to figure it out.
Try with another device using the VPN and try with your computer without the VPN.
Also I would suggest to check if this isn’t related to your wifi or router configurations/setup. Once I had a router that sucks a lot and for once in a while I had to reconnect or even restart the router to make it work again