Best ways of using btc

I want to open a btc wallet because bitcoin is supposed to be completely independent. However all I see is third parties making wallets and apps and that to me beats the point of using btc. So my questions are as followed: 1. How do I create my own wallet? (no third party at all as was intended originally) 2. Do I need to download a node for it on my pc? 3. How can I keep my bitcoin offline and only transfer specific amounts when I choose. 4. Can I transfer from any device if I have the key or do I need my main pc/node to make the transaction? 5. Do the wallets matter or do I just need the private key that they generated at the beginning? 6. Is there a way to buy bitcoin for usd or other currency that is secure and can guarantee the transaction? I heard about bisq being a good option but don’t fully understand it yet.

Big thanks to anyone who can take the time to help me here And if you know a place with good videos that get really in depth onto the entire process from start to finish that would be great. (Again no third parties involved)