You asked
Is the sigma 20 200mm f 3 5 6 3 dg contemporary good for landscape?
Here is what the site says about that.
From Sigma 20-200mm f/3.5-6.3 DG Contemporary: Sigma 20-200mm f/3.5-6.3 DG Contemporary: A zoom lens by Sigma for Full frame cameras, 20-200mm f/3.5-6.3. A 10x full-frame travel zoom that starts at 20mm. Specs - Maker: Sigma - Focal length: 20-200mm (zoom) - Maximum aperture: f/3.5-6.3 (it gets darker as you zoom in) - Made for: Full frame sensors - Mounts: Sony E, L-Mount - Stabilised: no - Autofocus: yes What it frames like - On full frame (Sony E, L-Mount): as marked, ...
From Landscape: Landscape: Landscape photography is slow. The light does the work, the scene doesn't move much, and you can use a tripod. That changes what matters in a camera.
Quoted from this site's pages.