Theraflu and Polopiryna S do not affect the contraceptive efficacy of Slinda. You can take 1-2 Theraflu tablets every 4-6 hours, and if fever and pain persist, you can take Polopyrine S between Theraflu doses.

The dosage for Theraflu Complete is 1 or 2 tablets every 4 to 6 hours (maximum 8 tablets per day); Polopyrine S: 300 mg to 600 mg (1 to 2 tablets) every 4 hours. Do not take more than 3 g per day.

Here you can compare the prices of these drugs in online pharmacies and place your order with home delivery or pharmacy pickup:

https://www.gdziepolek.pl/produkty/127646/theraflu-complete-tabletki-powlekane/apteki

https://www.gdziepolek.pl/produkty/63063/polopiryna-s-tabletki-rozpuszczalne/apteki

In cities such as Warsaw, Wrocław, Katowice, Kraków, Lublin, Gdańsk, Łódź, Szczecin, Białystok, Poznań and Chorzów, products can be ordered with instant delivery in as little as 1 hour thanks to the Wolt Drive service.
Check if the service is available in your location: https://www.gdziepolek.pl/koszyk/szybka-dostawa?src=zf

I've attached links to helpful entries:

https://www.gdziepolek.pl/artykuly/jakie-leki-oslabiaja-skutecznosc-antykoncepcji

https://www.gdziepolek.pl/artykuly/jak-szybko-wyleczyc-grype

Here you can check the availability of Slinda in pharmacies and make reservations:

https://www.gdziepolek.pl/produkty/101505/slinda-tabletki-powlekane/apteki