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Now we have the crucial part. After having chosen the shop to target, how does PayPal method works?

Generally speaking, you file a Dispute through PayPal's Resolution Center, thereby the buyer & seller attempt to resolve the matter between themselves. This obviously won't happen, hence the Dispute will be escalated to a Claim.

PayPal then takes over by reviewing the case, and ultimately decides the outcome. If that fails, you can perform a chargeback through your credit card provider or a bank reversal via your bank/financial Institution.