can this game only be bought with paypal or is there a another way to buy it
Short answer: No, Itch blocked using Visa & Mastercard due to their threats from before.
You can still pay with Visa & Mastercard through "Pay with Paypal".
Select the option, then on the next page hit "Continue as Guest" (or similar), then it will ask for your email address. Put in an address and it will let you use a credit card to pay.