Bitcoin runs on a blockchain, blockchain is a software, blockchain runs on multiple nodes all across the globe, therefore first no one can bring it down, second it can not be tracked from where did the money came and where did it go.
For any of the myths that you have you should read good books about cryptocurrencies, follow fellows who are bitcoin evanglist like Jameson Loop -
https://lopp.net/bitcoin.htmlHe got a curated list of all good articles for beginners, including tutorials.
Now I will tell you about exchanges -
There are two type of exchanges, centralised and decentralised, it is almost impossible to use a decentralised exchange. Hence people use a centralised exchange.
Decentralised Exchanges - IDEX, Etherdelta, KyberNetwork etc.
Centralised Exchanges - Binance, Bittrex, HitBtc etc.
Then there are custodial and non custodial exchanges, custodial are those who store your currencies with them, try to avoid custodial exchanges considering they do not provide you your private key(kind of bank account password) and there has been many cases of custodial accounts being hacked in past.
Prefer to use wallets like Trezor/Nano or meta mask for storing ERC20 tokens, keep your private keys safe with you.
Use Non Custodial Exchanges like -
CoinSwitch exchange (highly rated for me), they have 400+ coins with them, and they do not store your currencies with them.
Changelly, Shapeshift are few other examples of non custodial exchanges.