You have the possibility to buy someone's ticket by signing up on the waiting list. Waiting lists can be found on the Shotgun app. Go to the page of the event you want to go to, at the bottom of the page there is a green button that invites you to "Join the waiting list".
By singing up on the list, if your credit card is not registered and you will receive an email as soon as a ticket is available and you will have 10 minutes to buy it. If your credit card is registered and you have selected the automatic purchase, the next available ticket is released and will be purchased automatically, you will then receive your ticket and the receipt by email. You are not guaranteed to find a ticket by registering on the waiting list, it depends on resales! Please note, waiting lists are at the Organiser's discretion, and are therefore not always available for all events. Here is the link to the app here.