some very basics – Sorry if this has been asked a million times already

Hi, I am trying to figure out mining. After 10 days of mining RVN, I have around 550 coins. Cool. Now I would like to mine for the future, not for trading. Since I am a complete noob, I would like to understand few things.

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I use minerstat to mine RVN coins with a 3080ti , and I have a wallet called AtomicWallet. So my payouts go to this recieving adress.

Question 1 : Is it safe to leave your coins somewhere on a server (since they have your secret phrase, your password all the info they can get).

Question 2 : Is it possible to physically download your coins for a deep storage once mined ? and to make this process off the grid ?

Question 3 : What happens if AtomicWallet disappears ? Are all the coins lost ?

Sorry again for the noobility level and thank you for reading 🙂