I’ve been doing it for years and never had a problem but people write bugs! The trick, as a beginner, is to use well tested contracts and compose them. But fuzzing/static analysis tools are helping move the industry forward leaps and bounds too! So give it a few years and the space will mature.

It depends. If you use software with many years of stability, it's safe (Bitcoin has a 9 year uptime). There are some very reputable companies, like Casa or Unchained Capita that help you store your money safely using multisig contracts and hardware wallets very safely without trust in them.

With newer, faster changing software of course the risk is much higher, so I'm not comfortable using them, but many people take that risk.