At the outset, it should be noted that the drugs mentioned in the question: Bupropion and Fluoxetine are subject to prescription, so the legitimacy and need to combine them in therapy should be determined by a doctor. This combination of drugs can be used, but you should strictly follow your doctor's instructions and observe your body's reactions.

Both drugs affect the levels of neurotransmitters in the brain and may increase the risk of serotonin syndrome and seizures, especially in people with a predisposition.
Serotonin syndrome manifests itself, m.in, confusion, agitation, fever, sweating, ataxia, hyperreflexia, muscle clonic seizures, and diarrhea. This condition is distinguished by the so-called triad of symptoms, which includes:

Vegetative disorders, i.e. increased blood pressure, fever, diarrhea, vomiting and pupil dilation.

Psychiatric symptoms, consisting of anxiety disorders, feelings of anxiety and confusion.

Neuromuscular ailments, i.e. recurrent cramps, pain and increased muscle tone.

The dosage should be individually adjusted by the physician and the patient should be monitored for side effects such as agitation, insomnia or cardiac arrhythmias. Therefore, if you observe such side effects, you should inform your doctor, who will decide on further treatment on this basis.

If you need more personalized advice, you can use teleconsultations here:

https://www.gdziepolek.pl/telekonsultacja

Through Gdziepolek, it is possible to book medicines in a selected pharmacy in Polish:

https://www.gdziepolek.pl/produkty/30651/fluoksetyna-egis-kapsulki/apteki

https://www.gdziepolek.pl/produkty/112437/bupropion-neuraxpharm-tabletki-o-zmodyfikowanym-uwalnianiu/apteki