mpu9250-yaw angle

hi all, i am new here so my question maybe stupid

i have a mpu9250 i was able to get the pitch and roll angles and filtering them with the accelerometer
my problem is with the yaw angle i found it but it keeps drifting alot

i have read that there is a way to filter it with the magnetometer or combat the output

anyone knows how to ?
please help

PS. my code is attached

sketch_nov23a.ino (7.79 KB)

Do not double post. Your question was answered here.