Testing PayPal express

I know someone has asked and resolved this but I can’t find the thread. Sorry for the repeat!

I’m now testing the registration process using PayPal Express. Questions:

1) I can’t find any information about how to set up things on the PayPal side. I’ve looked and looked in this site and others but I can’t find clear answers. What exactly do I do in Sandbox? I set it up, created a preconfigured account as well as API and Payment Card credentials. But when I test, nothing really happens.

2) When I test a dummy registration, the ‘subscription’ paypal button appears but when I click on it, it sends me to a Sandbox window where it’s unclear what to do. The membership/subscription is created on my wp site but as a ‘free’ subscription. Does anybody know why or what am I doing wrong?

Does the sandbox actually work just like a live site?

Any help would be greatly appreciated!!