So I just learned about Robosats and it looks like a really nice way of doing P2P. However, it works through the Lightning network, which I don't have much knowledge about. I have read that I could use wallets like Phoenix or Breeze, but how do I move my funds from on-chain to LN and the other way around?

I have also read some complaints about these wallets because of the opening channels fees. What is this exactly?

Thanks for your help.