Use cash if possible. But you can also pay quickly and easily at store checkouts with anonymous voucher cards that others buy for you.
If you want to pay with other cards or your smartphone, you should primarily use your bank's card or app.
In any case, avoid third-party payment service providers such as Apple Pay, Google Pay, Amazon Pay, PayPal or Klarna. This is because they also analyze your shopping behavior.
It is better to process money transactions directly with your own bank. Also bear in mind that some providers such as Klarna may be able to view your other bank account transactions.