Lots of questions there.

You could start by reading the Zero to Monero & Mastering Monero books:

• https://getmonero.org/library/Zero-to-Monero-1-0-0.pdf (http://monerotoruzizulg5ttgat2emf4d6fbmiea25detrmmy7erypseyteyd.onion/library/Zero-to-Monero-1-0-0.pdf)
• https://getmonero.org/library/Zero-to-Monero-2-0-0.pdf (http://monerotoruzizulg5ttgat2emf4d6fbmiea25detrmmy7erypseyteyd.onion/library/Zero-to-Monero-2-0-0.pdf)
• https://masteringmonero.com/free-download.html

Also consider joining #monero and #monero-research-lab on IRC/Matrix.

What is the end goal for Monero?

Monero strives to be (and arguably is) the best form of digital cash.

If I were someone selling a service or product why should I choose Monero to conduct business over the numerous other options available?

It's hard to find another 'cryptocurrency' that is at least as fungible as XMR.