Using "for" for a period of time (for 2 years) and "since" for a starting point (since 2021). Articles: Overusing or omitting "a," "an," and "the".
Using much, many, a lot of, a few, and a little correctly with countable and uncountable nouns. Grammar in Use - Pre-intermediate
The core of pre-intermediate grammar is learning to combine different time frames. Using "for" for a period of time (for
Forgetting to swap the subject and verb (e.g., "Why you are late?" instead of " Why are you late?"). Say vs. Tell: "He said that..." vs "He told me that...". " and "the". Using much