That depends on who you bought from and in which capacity. There are three cases.

As a consumer from a trader: you have a 14 day right of withdrawal from the day the goods arrive, without giving any reason. The full withdrawal notice including the model withdrawal form is in your order confirmation and on the seller profile page.

As a business from a trader: there is no statutory right of withdrawal for business transactions. Whether you can still return depends on whether the seller voluntarily grants a return right.

From a private seller: private sales have neither a right of withdrawal nor a statutory warranty. Panterzone tells you before the purchase that the seller is a private individual.

You must declare your withdrawal; sending the goods back without a word is not enough. An unequivocal statement is sufficient, for example an e-mail to the seller. What counts for the deadline is when you send it, not when it arrives.

The seller reimburses all payments including delivery costs at the latest fourteen days after your declaration reaches them, using the same means of payment you paid with. They may withhold reimbursement until they have the goods back or you have provided evidence that you sent them. You must send the goods back within fourteen days of your declaration.

You may examine the goods the way you could in a shop. You are only liable for a diminished value if it results from handling beyond that.

Under Orders you can request a refund for each order line. If the applicable deadline has passed, the message tells you why it is no longer possible. Your statutory warranty rights for defective goods are unaffected in all cases, they are something different from the right of withdrawal.