BTC payment system

Hello,

I need a mobile app that supports lightning network to get paid with BTC as I think this will attract curiosity in my local business.
But I have no idea what can I use and how Lightning network differs from the BTC network. I would apreciate if someone can put light on my questions

Is there any app where I can manage from a computer and allow my employees to send and recieve payments with a QR code.

Can I convert to USDT with the same app? and send stables to and exchange?

how does LN work from an adress point of view? can I send BTC to an LN adress with no problem?

What else should I know or what should I research??

I have heard of this https://docs.btcpayserver.org/ , but it looks too complicated and I think I can't use it in a mobile phone. Any advice about this?

Also heard about Breeze wallet as POS, has anyone used it?

I feel quite lost right now, and maybe the easyest think to do is to download bitpay app. Thanks in advance!!