You asked
Is the canon eos 5d mark iii good for beginners?
The Canon EOS 5D Mark III is a capable camera, but I'd call it a second step rather than a first one. It's a full-frame DSLR from 2012 with no stabilisation in the body, so you'll want stabilised lenses for slow shutter speeds. Its real strength is that it's a common used buy, and it fits a huge range of Canon EF lenses.
If you do pick it up, start with something versatile and affordable, like the Canon EF 24-105mm f/3.5-5.6 IS STM or the Canon EF 50mm f/1.8 STM. For general advice on choosing a first body, see Your first camera, and for buying secondhand, see buying used.
Written by Claude from this site's pages.