Is it safe to keep your all crypto currency at a single exchange (bitfinnix)?Or one should choose multiple exchanges.
Storing your stash of cryptos on an exchange is not even recommended in the first place. Only do so If you're an active trader and only keep a percentage of your holdings on the exchange. While dealing with Cryptocurrencies is interesting, one major downside is the security. In just one clean swoop, you can lose everything (Your profits, capital) etc. You've to take it seriously so. Just get a personal wallet instead.
Personal wallets are good, but they don't seem to be suitable for daily traders, so you should have several different markets,
and choose a market that has high confidence, so the security level is also good.