You asked
Is the sigma 24mm f 2 dg contemporary good for landscape?
It's a decent pick, but the f/2 speed isn't what you need for landscapes. Most landscape work happens between f/8 and f/11, so you'd be paying for a fast aperture you'll rarely use. On full frame, 24mm is a useful wide view for big skies and foregrounds. On APS-C it frames like 36mm, which is too tight for most landscape scenes.
If you want a landscape prime, the Sigma 24mm f/3.5 DG Contemporary is a pocketable wide option that suits how you'll shoot. For flexibility, a wide zoom is the classic choice, as covered in landscape lenses. The Sigma 24mm f/2 makes more sense if you also shoot low light or people.
Written by Claude from this site's pages.