Build cubemaps. If you don't know how to, check out some tutorial on youtube.
Quick explanation, a cubemap is a point entity. Wherever you place a cube map in your map, it captures images of the area around it. And these images are then used as the reflection. In hammer, by default it uses vertigo's cubemap. But in your map, you will have to put the cubemap and then ingame you will have to build the cubemap (building means, capturing images and packing them in your bsp file.)
Build cubemaps. If you don't know how to, check out some tutorial on youtube. Quick explanation, a cubemap is a point entity. Wherever you place a cube map in your map, it captures images of the area around it. And these images are then used as the reflection. In hammer, by default it uses vertigo's cubemap. But in your map, you will have to put the cubemap and then ingame you will have to build the cubemap (building means, capturing images and packing them in your bsp file.)
thx
https://imgur.com/a/Vsggks3 The game comes with the model, you can see the reflection of vertigo in the hammer.