You can use vedic maths for easy multiplication .and the other think is that u must practice with numbers
minimum 20 problems of multiplication each day without fail
Memorise the first 10 numbers on the scale

Memorise the order of the operations if u did not follow this order then the sum might be rong the order is 1.Parenthesis 2.Exponent 3.Multiplication 4.Division 5.Addition 6.Subraction

Start off with multipliying with 1

Then with 2 remember multipling with 2 always used to be double

then with 3

then with 4

then with 5 

Multiplying with 6-9 is same as the pst 4 nos

any digit multiplied with 10 should have a zero at last no digit changes