One thing in particular that bugs me about what Americans say and how they say it is their complete disregard for adverbs.
For those who have forgotten since fourth grade, adverbs describe how something is done. The very name is a portmanteau of adjective (describing how) and verb (something is done).
For example, if I run down a hill and I do so with some speed, you might say that I have run down the hill quickly. I did not “run down the hill real quick“. Similarly, if I don’t know the rules of grammar, you might say that I don’t know how to speak properly. It is not the case that I “can’t speak proper“.
Adverbs help add color and imagery to an otherwise factual description of something. They are distinct from adjectives and should be treated as such. I can be quick and I can run quickly, but I cannot run quick.