Okay, so imagine you have a toy that you really like and you want to share it with your friend. But your friend is a bit bossy and wants to keep the toy all to themselves.
Now, you have a choice to make: you could either keep asking for the toy back and get into a fight with your friend, or you could surrender the toy to them first and then ask them nicely to share it with you.
In this situation, surrender means giving up something you like or want to someone else. And regrant means asking for it back but in a nicer way, so that the other person is more likely to share it with you.
Now, in grown-up situations, this might happen with land. Let's say you own a piece of land, but the king wants to take it for himself. You could try to fight and keep your land, but that might not end well for you. So, instead, you surrender your land to the king and hope he will be kind enough to give it back to you later. That's what surrender and regrant means.