i had tried random forest ,logistic regg,and knn
and also tried to drop columns according to correlation and feature selection but maximum i got only is 78%
now what should i do
to increase accu.
How to increase accuracy
78% accuracy with knn, is near saturation, so well done this is sufficient. If you still want to achieve more accuracy you need to use more complex algorithms, deep learning etc.
Happy Learning 
i tried using mlp but not much effective