A) Please tell me which one is fine
1) Iíve decided to study in earnest then before
2) Iíve decided to study in earnest
B) IsĒ backlogĒ countable?
1) is wrong
2) is grammatically ok, though I'm not sure 'earnest' works well here. 'seriously' seems more natural. Teachers to confirm....
'backlog' is said to be countable in the dictionary.