I'm Planning to go to seiberia in December, taking my cameras there would they work in -20C -30C?

Nikon D5300 and Gopro 5 Black are the main two.

I would not take them out in wet / rain conditions… Just when it dry but cold?

would they work? I would take care of the condensation and battery

Learn how to spell before anything else or you might end up in the wrong place.

They will work just fine, but the condensation and battery issues may be harder to deal with than you think. Batteries may last only 10% or less of the time they normally do. You may need to purchase larger battery packs or even an usb battery you can put in your jacket and connect to the camera by wire.

The GoPro should be ok, even better if you have it in it's weatherproof housing. The Nikon may have problems with the zoom, as the lubricant will solidify. Batteries will have low performance. The other problem is bringing a very cold camera into a warm and more humid environment, ie when you bring it indoors. That will cause condensation, some of it internal. I would take a few good ziplock bags, and if possible some silica gel packs to keep the camera dry till it warms up

I've used my Nikon DSLRs in -18°C temperatures for full days. The camera was kept at ambient temperature. Going down to -30 may be more challenging and you may want to keep the camera inside your jacket when not in use. Electronics doesn't work well below -30°C unless specifically designed to do so. Plus, battery life is reduced and lubricants thicken. Condensation may be an issue if you keep it in your jacket. To conserve battery life, don't use live view. Use the optical view finder.

When entering a building, put the camera in a sealed plastic bag outdoors, then, let the camera warm up inside for at least 45 minutes. This prevents condensation on the camera. Bagging the camera outdoors ensures that the outdoor dew point temperature in the bag is preserved.

Since snowy scenes are likely, you'll either need to shoot in manual exposure mode or use exposure compensation if shooting in some sort of auto mode (program, aperture priority, or shutter priority), perhaps +1.0 to +1.7 EV. If you don't, your snow will be grey and everything else will be too dark. This is where the histogram is an invaluable tool.

If you don't know how to use exposure compensation and/or the histogram, learn before you go on the trip. Your manual has this information and there are plenty resources on the Internet, including how to shoot in snowy conditions.