Confusable Words “too” and “very”

‘Too’ and ‘very’ are not always the same.
‘Too’ means there is a limit, or a maximum:
“I can’t buy it because it is too expensive.” In this case ‘very’ is also ok.

“I’m sorry I’m too late.” In this case, it means the meeting time has finished.

However, if you mean “I am very late”, then don’t use ‘too’. For example, if the lesson starts at 7pm, and you arrive at 7:20, you can say “I’m very late,” but NOT “I’m too late.” If you arrive after the lesson has finished, you are ‘too late’.