I'm Ann, from the team here at Shopify :)
When it comes to PayPal, there are some cases where you can let customers checkout without a PayPal account. This is a setting you would have to turn on in PayPal directly. You can see the steps on how to make this happen on this page in our Shopify Manual, however, if you're having trouble following them, you will need to reach out to PayPal's support team directly. It might be that you're located in a country where this isn't supported, so it's best to reach out to them. You can find their contact information here.
That said, if you only want to take payment through PayPal, there are plenty of people all over the world who use PayPal, so that's fine. However, if it's possible for you to set up PayPal and a credit card payment gateway at the same time in your store, that gives your customers more ways to pay you, and it might help lead to less abandoned carts. If you're unsure of what other payment gateways you can use, let me know what country you're located in and I can send you a detailed list!
I hope this helps! If you have any more questions or concerns feel free to reach out to us on this thread :)
Have a great one,