Hi@Marius1234,

The slow VPN speed on the TP-Link Router when using the VPN Server or VPN Client is often due to the limitations of the router's CPU. The processing power of the router is not as robust as that of a computer or other devices, which can result in slower performance when establishing VPN connections. This limited processing capability of the router is a contributing factor to the slower speeds experienced. To improve VPN performance, you may consider setting up the VPN connection on a computer or other devices that offer more processing power and performance capabilities.
Alternatively, you might attempt to set up WireGuard VPN, which is noted for being faster than more conventional VPN protocols like OpenVPN, if your TP-Link router supports it.