そんなに謝らないで(そんなに謝らなくていいよ)って英語でなんて言うの？

As always there are many ways to express certain thoughts or ideas, any of the three listed above are sufficient.

No worries! There's no need to apologize. This is a common and informal way to say that there is no need to apologize. Person: "I'm so sorry I stepped on your shoe!" You: "No worries! There's no need to apologize." Don't worry, you don't have to apologize so much. This is a semi-formal expression letting the person know that they do not need to apologize so much. Person: "I'm so, so sorry I was late. Again, I'm so very sorry." You: "Don't worry, you don't have to apologize so much." It's no big deal, so there's no need to be sorry for that. This is a more formal way to tell someone that they do not have to be sorry for something. You can also modify this expression and say, "It's no big deal, so there's no need to apologize so much." Person: I am so sorry! I didn't mean to spill my drink on your shirt!" You: "It's no big deal, so there's no need to be sorry for that." OR Person: I am so sorry! I didn't mean to spill my drink on your shirt!" You: "It's no big deal, so there's no need to apologize so much."

It may be a slightly British trait that we apologise very quickly and maybe too frequently - sometimes even when it is not our fault! However, profuse and repeated apologies when there is little reason to apologise, may appear strange and unnecessary. "I'm really sorry about..." "Really, it's not a problem. There's no need to apologise!" Or, "Oh dear, my Skype has a bad connection. I'm so sorry about that." "It's OK, don't apologise!"

To tell your teacher that they don't have to apologize so much, you can say: "There is no need to apologize." "You don't have to be sorry." "Don't worry, it's okay."

If you want your teacher to know that he/she does not need to apologize that much, you can say the following to him/her. 1. No need to apologize. 2. These things happen sometimes, there's no need to apologize. Hope this helps!

Even though you may don't like it but try to be nice towards your teacher and stress that you understand their position and then say that you don't like it

"That is not necessary." This means that you are telling the teacher that it is not important for them to keep on apologizing.

"Don't worry. There's no need to say you're sorry." - In this sentence you are saying "Don't worry. " When using this phrase you are putting your teacher at ease. You are telling him/her not to stress about what she has said or done. "There's no need to say you're sorry" - When making this statement you are telling your teacher that he/she does not have to say he/she is sorry about the certain situation. It's okay, you don't have to apologize. - Using the phrase "It's okay" means you are telling your teacher that whatever he/she has said or done, that its okay with you. She has no reason to worry because he/she has not offended you. "...you don't have to apologize." - In saying this you are telling your teacher that he/she does not need to say sorry for anything because he/she has not offended you.

Many times if one is not so familiar with the preferences of a person who is not a close acquaintance, apologies can imply one is worried about offending the other person. Telling the person who is apologizing so much to relax may help to decrease the worry, and he/she may not continue to apologize so frequently. Another term meaning not required or necessary is "not needful."

Some good advice I once received is to rather say 'thank you' instead of sorry too many times, for example; "Thank you for your patience, I was late because I was stuck in traffic." not "Sorry I was late because Iw as stuck in traffic." "Thank you for understanding" not "Sorry about that."