Comprehensive grammar Diagnostic #2 (from "mycomplab.com")

Unfortunately, I didn't pay much mind to the first diagnostic I went through and I got frustrated in attempting to find the analysis of that first one. I did go through another one earlier today (Sept. 8th).
I am deficit in:
sentence grammar--pronouns cases and references; subject-verb agreement; misplaced and dangling modifiers
basic grammar--pronoun cases; verb forms
usage & stule-- parallel structure; eliminating redundancy; "should have"[inferences from speech]; faulty comparisons; "would have"[inferences from speech]
punctuation & mechanics-- commas with restrictive and non-restrictive clauses; commas with possessive pronouns
Of the 50 statements/questions, I got 60% correct.
As someone who enjoys writing, I'm surprised that, in English mechanics, I'm lousy!!