Do you have any more tips how to cure a acute blocked nose (or just get a momentary relief) without using nasal spray or warm salty water?

Steam. If you heat water in a pan until it is steaming. Place a towel over your head and (keeping your face away from the pot), allow the steam to go through your nostrils. Do not burn yourself. If you want a less risky option, try taking a hot shower and allowing the steam to build up.
Take a pill. If you are otherwise healthy, have no diabetes, high blood pressure or thyroid problems and you are younger than 60, you can take an otc decogestant by mouth, such as phenylephrine 10mg or Pseudoephedrine (now behind the counter) 30-60mg every 6 hours for a few days.
Pull your nose. If you pull the outside of your nose/cheek border toward your ear, this helps to open up the nostril area and can temporarily relieve stuffiness. Warm salt water (saline spray or irrigation) is also very good. Nasal spray, like afrin, (oxymetazoline) must be used judiciously as it can cause dependency if used for more than 3-4 days in a row. Sudafed can also help, but don't use if you have any contraindications!