i'm new so sorry if my Questions is in the wrong category can anyone Recommend a modem or router wifi that Support any vpn protocol for example openvpn-pptp without slowing down internet speed.
The number of supported xDSL modems is much less than supported routers, due to unavailability of drives. looking for a supported modem or modem-router will significantly narrow down your choices. So, if you have a good device provided by your ISP and you don't mind having two devices, you may just get a router for OpenWrt and connect it downstream of your ISP modem or modem-router (which you could set in bridge mode).
The list of supported hardware is here https://openwrt.org/toh/views/toh_available_864. So if you know what you are looking for you can check it. Otherwise you will need to be more specific about That will your internet speed (and your other requirements such as media server etc), so that people can help you.
...and your internet speed is...?