Why didn't you continue these questions in
How to have reasonable privacy safely when paying??
3) After you decide an amount (let's say, $1000) then you have to mix this amount
Why? You're saying this as if it's a given, but it totally depends on who you're trying to hide from, and how your current funds are "distributed" (just one UTXO, or many).
-Mixers: This is what im familiar with. But I want to learn how Coinjoin works since stupid authorities now think anyone that wants privacy is automatically suspect of doing something wrong.
That depends on your country:
A cryptocurrency mixing service is not necessarily illegal. It is an online service that allows users to disguise the origin and destination of cryptocurrencies.
I like my privacy, but I don't like paying 2-5% mixing fee. My satoshis are too valuable to waste them like that.
-Non KYC exchange: Register in a non-KYC exchange with Tor, send coins, and send them back to another address. This should add a reasonable amount of privacy. Im not familiar with such exchanges.
They may not know who you are, but you should assume they keep all transaction data for many years. As always, the level of privacy gained depends on who you're trying to hide from.