How to Use both DNS and VPN

For DNS, I use NextDNS by systemd-resolved. For VPN, I use ProtonVPN. I cannot connect to internet when I’m connected to VPN. How do I solve this?

Specify a custom DNS:
How to use custom DNS | Proton VPN

Here’s the address you can use:
systemd-resolved.service: Network Name Resolution manager | Man Page | System Administration | systemd-resolved | ManKier

If the issue persists, disable the kill switch:
How to use advanced kill switch | Proton VPN