Simple Linear Regression-----How to make my model more efficient??
You cannot really do much: the fit of the regressor is optimum, therefore it is the best that the algorithm can do given these points. What you can do, is change the weights of individual points of the dataset using the sample weight parameter of 

LinearRegression.fit(X, y, sample_weight)


method, to "attract" the line towards them and see how this affects the accuracy.

I would not expect notable difference because your data do not follow a linear pattern.