It is still winter in Beijing, but not so chilly. It is reported that the temperature could be around 5~10C, so a light down jacket and sweater is ok for going outside. You could go to the Great Wall at anytime currently. My suggestion is that you visit Badaling Great Wall. As for the details of great walls in Beijing, please turn to: https://www.travelchinaguide.com/china_great_wall/scene/beijing/

Yes, it is still cold at this time but much better than in winter. You need to take some clothes such as sweaters, coats, jackets, which may prevent you from the strong wind, especially when you go to visit the Great Wall.

As for the Great Wall, i suggest the most popular Badaling Section or the splendid Mutianyu Section. Both are wonderful.