Ripe and mature Palm fruits. Boil soft and pound to get paste, remove some palm oil, then filter to get banga Sauce. How do I get a long shief life Preservative.?
If this is for a commercial product, talk to a distributor/maker of preservatives directly and discuss your exact product - be prepared for them mandating changes to the recipe. They will also know what your local laws (and the laws of any intended target market) allow or do not allow.
Consider consulting academic/professional literature on food preservation - but in the end, unless you are formally trained expert in these things, it is best to keep the responsibility with the food additive maker as much as possible.
If this is for home preservation, if no known good recipes for a shelf stable version exist, the effort needed to create one is not unlikely to be too high to be worth it - and mistakes when experimenting with chemical preservatives (benzoates, nitrates....) can yield harmful product that makes you or your family sick.
There is no "stir in enough poison to make bacteria dead and leave us alive" solution that works for all foods and storage conditions. Using a chemical preservative in the wrong way can result in a product that does not visibly spoil but turns poisonous (eg by botulism) because you killed everything that could stop it from doing so - or which is poisonous due to overdosing the preservative.