Call Center English Conversation: Mock Call for Health Insurance | Single Step English

I am so grateful!!! Tysm!!!

My sir,
Could you please tell me my meaning is correct? Are these sentences grammatically correct?
Here can I use interchangeably while and when?
1) When I was reading the book power went off.
2)While I was reading the book power went off.

3) I was reading the book when power went off. Here meaning I started reading when the power went off right?

4)I will call you when you come here .

Even I can use two past tenses sentences using when as well yah?
5)when I went to washroom my friend came to my home .

My sir,
Could you please tell me are these sentences grammatically correct?

1)I don’t want to interfere into your problem
2)I don’t want to interfere in your problem
3)I’m not interfering into this
4)I’m not interfering in this
Are these sentences grammatically correct

Due to my health issues i couldn't watch your last videos sir. Just saw this lesson video again awesome sir. And i have few questions i will note it down and will request you to do a video😊😊

My sir,
Could you please tell me are these Sentences grammatically correct?. TO OR ON
AFTER ADD WE TO PREPOSITION YAH?
1)Do I have to add red price on a sale item?
2)Do I have to add red price to a sale item?

I work at store in this situation I'm not a customer

Good one sir