Nikon 50mm 1.8 or Rokinon 85mm 1.4?
I already own a 35mm 1.8 Nikon and use it mostly for portraits and street photography, however, I want to try a different focal length, I think it should be interesting. The 50mm is good, the aperture is great, but I don't know if I'm gonna be working in almost the same range of the 35mm one. The 85mm would be a fine choice because I have never worked with a lens with that focal length, and it requires me to do things I want to learn like metering. I'm interested in learning, but I don't know if the 85mm is a good choice if I'm gonna be using it for portraits and street photography.
The 85 mm is a fine portrait lens if you have a full frame camera, like a 35 mm SLR or D3/D700 series dSLR. The 50 mm lens is considered THE portrait lens for Nikon cropped sensored cameras.
Actually the street photographers I know use a 35 mm lens on a 35 mm rangefinder camera. If you have a cropped sensored dSLR, that would be equivalent to about a 24 mm lens. Even your 35 mm lens is a little too long to shoot "street" photography, the 85 mm is certainly too long to get those intimate, all in focus street photos that describe the genre.
I think you may want to visit this site and see what field of view each focal length will give you.
85mm will work well for what you want. However, manual focussing on a f1.4 will be a challenge. I'd say look for a used 85mm f1.8 AF