There are many English words that even native speakers confuse!
It’s (it is) / its (possessive of it)
There (a place, not here)/ They’re (they are)/ Their (possessive of they)
Your (Possessive of you)/You’re (you are)
To (preposition of direction towards -or- particle in infinitive “to go” “to see”)/ Too (excessively “too much” -or- also “me too!”) / Two (the number 2)
Then (time after – the next thing you’ll do). Than (comparative. Bigger than what? Taller than who?]
Here are many others including principle (value/moral) vs. principal (first/leader) and accept (receive willingly) vs. except (not that one, the exception).
Homophones (same sound, different spelling)
Deborah’s Vocabulary handouts on Have, So and That