It doesn't really mean to let someone speak. It means when your friend is talking too much and you don't have a chance to speak. You can say "please let Tom have his say as well" or " please let Tom say what he has to say" Hope it helps 😊

Yes, as the other have said . . . It's a funny expression. It means that other people are talking so much that none of your words would fit, so they have to turn sideways and try to fit that way, as if you had to turn sideways and hold your breath to get through a narrow space. It's all figurative, but very descriptive.

Edgeways. It means the other person is speaking a lot/too much and there is no space/room for you to speak too.

Yes you can. But careful with the spelling; it's To get a word in edgeways.

Hey Arkadiusz, "to get a word in edgewise" has a different meaning. It is used in situations when so many people speak, and it's hard to get a chance to speak. For example, after the lecture, many people had a question that it was hard to get a word in edgewise.