Just off out, so I'll be short and sharp.
It all depends on why you want to get better at hills i.e. climbing, trail running, fell running, hiking for fun... :)
Some things that can help:
Muscular endurance: gives quick and dramatic improvements, but don’t overuse. This means doing things like box step-ups, front lunges, split jump squats and squat jumps. 10 reps each for up to 6 sets work well. Progression over weeks can be: body weight, body weight + 10%, body weight +10% but reduced rest period, bw + 15% etc etc. Your legs will hurt for some days afterwards before you get used to it.
Reverse pyramids: run 45s uphill, walk down, then 30s up, walk down etc: reverse pyramids are more enjoyable than normal pyramids for an interesting reason that I won’t go into detail here. Same work capacity, but different experience.
Hill bounding. This is a specific technique that can be found online.
The steeper the hill, the more it’s strength training rather than muscular endurance. Adjust according to what’s important at the time.
I’d also work on rucking with a weighted backpack up hills.