Could you please tell me whether or not ‘to,’ ‘lesson,’ ‘plan,’ ‘at,’ ‘had,’ ‘regularly,’ and ‘part’ are correctly used in my sentences below?

Could you please tell me whether or not ‘to,’ ‘lesson,’ ‘plan,’ ‘at,’ ‘had,’ ‘regularly,’ and ‘part’ are correctly used in my sentences below?

1. Five to seven days before Miss Gray has to deliver a particular lesson, the principal has to check her lesson plan.
2. At the end of the whole-day classes, the principal had a post-conference with each teacher, not to make him/her feel humiliated about any mistake committed, but to offer suggestions for improvement on his/teaching approaches.
3. Proper documentation is essential in teaching, and a teacher must regularly do it.
4. Documentation on everything that happens in a business might be rigorous, time-consuming on a businessman’s part, but it is absolutely necessary.