How to obtain a refund on PS4?


depends on your country, l guess.

google it (sorry) or call the support hotline and keep in mind, that Sony is especially bitchy about refunds.

state that the game is broken (defect) and that the publisher and developer are not providing a reasonable repair (the way it is done and the time are not specified). that is important. your product is defect and help or support is otherwise not provided, making a refund the only option left to you.
the seller has the right to refuse a refund on the base, that a repair is provided. the repair terms have to be specified, which focus does not do in any way (again, duration and content of repair)

that applies to consumer rights in europe, the americas won't differ much, l guess.