Dear Brother, If I miss Assar prayer can I offer it just before Maghrib although it is during the prohibited time? Jazakallah

AAWW

Yes, you should perform Asr prayer even just few minutes before Maghrib, as the prohibition of praying at that time - and in the other times of the prohibition of praying - is when praying an optional prayer that has no particular reason other than devotion to Allah swt. But if there is a reason, like to make up a missed prayer, or to pray a current one (like in your case), then praying is definitely allowed with no restriction or undesirability involved.