The advice part of the question is a bit general, but I'll try answering. I only have summer experience in the area. The local hub town is Interlaken. From there the valley splits in 2, left is towards Grindelwald, the right to Lauterbrunner valley. Those two are connected in altitude with a pass, cog trains run on both sides to Kleine Scheidegg station. The pass is overlooked by 3 big mountains, Eiger, Moench and Jungfrau. From KS it's possible to go up to Jungfraujoch station, a high altitude viewing/hotel/restaurant kind of place. It's not cheap and busy with tourists.

Grindelwald is quite big, with 2 train stops. I prefer the villages on the other side. Also the other side, the Lauterbrunnen valley is quite spectacular in itself. You can hike up to KS from Grindelwald, quite a slog, or take the train up  and walk down. From the other side I would start at Wengen, not lower. I would expect the trails to be in good shape as this is a very popular area but be prepared for a lot of snow, snowshoes or something to put on the soles of your shoes might be necessary.

Weather permitting, it should be quite spectacular.

https://www.jungfrau.ch/en-gb/winter-hiking/

https://heretotravel.com/winter-hiking-jungfrau-region/

Other popular places in the area are Schynige Platte closer to Interlaken and I really like the view of the Jungfrau massif in good weather from Niederhorn mountain on the other side of Interlaken. It's also supposedly a good hike down to Interlaken.