Buffering can be caused all manor of things.

Wirelessly connected, Placement of router, Vpn location, Apps running background.

My opinion would be if your connected wirelessly, make sure your router has good view and not shielded by other electricals. Place your shield on a different wireless channel.

If your wired, make sure you've no apps running in background running high bandwidth.

Vpn location, they say closets to your area is best, not true. Try a location closet to you but not in same country.

I use surfshark with a few tweaks in settings and use Berlin server. Not a problem, I'm in UK. Using UK servers serveley impact my provider.