Does yeast helps making soil more fertile/productive ?? i'm new in gardening and does not know how to plant seeds of diffrent fruits so what i did was to put the whole fruit inside the soil but to see some results i open up the test patch and found the fruit still decomposing after 2 weeks no where to found the roots or anything. so the question is Can i add up little yeast with them so they can decompose fast ???

you need to read a book on the basics of gardening and what seeds will grow where geographically. just burying a whole fruit is unlikely to result any time soon in a fruit tree. The yeast will have no appreciable effect on decomposition in this context.