If the cough doesn't break off, can I add Mucosolvan inhalation to Nebbud, Nasivin, protargol and GrinTuss syrup?

Mucosolvan does not interact with Nasivin, protargol or Nebbud and GrinTuss syrup.
However, it is a prescription drug, so it should be decided by your doctor. If you do not have the opportunity to consult a paediatrician, you can take advantage of the teleconsultation here:

https://www.gdziepolek.pl/telekonsultacja

It is important to inhale Mucosolvan no later than 4 hours before bedtime.

Here you can compare the prices of Nasivin and GrinTuss in online pharmacies and order for home delivery or pharmacy pickup:

https://www.gdziepolek.pl/produkty/51620/nasivin-kids-aerozol/apteki

https://www.gdziepolek.pl/produkty/33889/aboca-grintuss-pediatric-syrop/apteki

In cities such as Warsaw, Wrocław, Łódź or Białystok, products can be ordered with instant delivery even in 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

Here you can check the availability of Mucosolva and Nebbud in pharmacies and make a reservation:

https://www.gdziepolek.pl/produkty/50563/mucosolvan-inhalacje-plyn/apteki

https://www.gdziepolek.pl/produkty/52516/nebbud-zawiesina/apteki

It should be noted that after first opening, Mucosolvan for inhalation is suitable for use for 12 months.