You can take Olfen SR 75 mg during a course of Advantan. According to the information contained in the Safety Data Sheet of Advantan - "No reports of interactions of Advantan with other medicinal products."
The methylprednisolone in Advantana is absorbed into the systemic circulation to a small extent, therefore the risk of interaction with diclofenac from Olfen is negligible.

It is true, however, that another form of methylprednisolone (intended for oral use) should not be combined with non-steroidal anti-inflammatory drugs, such as diclofenac from Olfen, as this increases the risk of gastrointestinal side effects, including dangerous bleeding from the gastrointestinal tract or exacerbation of symptoms of gastric or duodenal ulcers.

Here you can check the availability of these medicines and make a reservation at the pharmacy:

https://www.gdziepolek.pl/produkty/2538/advantan-masc/apteki?pvid=242862

https://www.gdziepolek.pl/produkty/56590/olfen-75-sr-tabletki-o-przedluzonym-uwalnianiu/apteki?pvid=104463

I also attach a link to helpful entries:

https://www.gdziepolek.pl/artykuly/czy-sterydy-sa-bezpieczne

https://www.gdziepolek.pl/artykuly/jak-pozbyc-sie-tradziku-u-doroslych