The cold a baby gets is the same cold virus that adults and kids and teens get so the babies cold should last as long as anyone else's cold virus.
Most babies colds go away within 7 to 10 days but some more severe strains of the cold virus in a baby may last as long as 14 days and may come back as well.
If the cold lasts longer than 14 days or seems to be getting worse it would be best to take the baby to the doctor or the urgent care or the emergency room to make sure nothing else is going on that is more serious.
Usually though the babies cold will go away within 7 days which is what I've experienced with my own kids.
When a baby is congested the congestion should go away within a week or 10 days.
My babies congestion usually went away within 7 days but sometimes if the baby had a more severe cold and congestion it would sometimes linger on for 14 days which the doctor said was normal.
You can help the baby with the congestion by using a nose suction device or nose vacuum that is safe for babies or use a humidifier and also some saline spray or nasal drops that are safe for babies.
Although the baby has become congested and can have a bit of trouble breathing the baby can still breathe through their mouth so there's no way for the baby to actually suffocate from being congested.
Many babies become congested and although they have a bit of difficulty breathing they still can breathe enough to keep them alive and keep them from suffocating.
For the baby to die of not being able to breathe their airways would have to be completely or at least nearly completely closed off.
That doesn't happen during congestion so the baby is safe.
When a baby is congested you should use a humidifier in the babies room at night and during the day when they are in the room to add moisture to their lungs and nasal passages.
Also using a nose vacuum to suction out some of the mucus to help keep the babies nose clear can help.
Within a week or so the babies congestion should go away and the baby should be able to breathe properly again.
You can also give the baby some baby safe nasal spray or nasal drops to help clear the congestion.