Sadly I have to agree with RedxSkull. I started playing Black Ops 2 in the year of our lord 2015 - I was am outright child back then. I now pay taxes, and you can presume in the time between I have also suffered greatly under the thumb of better players but I eventually triumphed [in my own day].
One huge recommendation I'd make? Play the campaigns! Not just Black Ops 2 - World at War would absolutely beat into you how to effectively play within the "CoD" gameplay loop. I beat that shit on veteran, the best butthole clenching experience i ever had.