1-The best way to switch the currency in Poland , air port . exchange shops , banks ?
Exchange shops are a good option. If you have a bigger amount to exchange, like 1000 USD, negotiate the price. Exchange shops in the airports and train stations may have worse exchange rates than those in the city center.
I don't know how it is with banks, if their exchange rates are comparable with those of exchange shops, or worse.
Exchange shops are called in Polish "kantor", but they usually have English signs as well.
2-Can I use *. Euro * A US dollar
In shops, restaurants, etc.?
Big supermarkets sometimes accept euro, but they will have a bad exchange rate and you will get your change in the Polish currency. Definitely exchange the money to Złoty earlier.
Can I use the ATM card FOR CASH ? Is there a commission on use
It depends on your bank, the one that issued the card. If you have a card with free withdrawals in the whole world or Europe, it will be free.
If you withdraw the money from an ATM and it asks you about the currency of the transaction, don't choose the option with the "guaranteed exchange rate", select the option that you want that the transaction will be carried out in the Polish currency. The exchange rate of your bank/card operator/whoever is responsible for that will be better than the one offered by the ATM operator and showed to you.
Knowing that the Saudi riyal and the Polish zloty almost the same value
If you are from Saudi Arabia, then it's good for you.