誰が一番サウナに長く居れるか競争しようって英語でなんて言うの？

"Let's" is a great way to suggest an action to a group of people, especially friends. In this sentence, it is implied that longest means "the longest amount of time" so you don't need to say all of that. I hope that this helps. :)

Let's see who can stay in the sauna the longest! Using this sentence is daring your friends. "dare" who has the courage or who is brave enough to do something. Let's have some fun! Let's compete to see who can stay in the sauna the longest! "compete" to have a competition I challenge you to see who can stay in the sauna the longest! "challenge" to ask someone to participate in an action

phrases used often in a competition context, implying or starting the competition. "Let's see who lasts" is a very short way of initiating such a competition.

Let's see who lasts the longest in the sauna! Let's see who can remain in the sauna the longest! In these sentences "See" is used to talk about an experience you will witness. You will be there to watch or see who comes out of the Sauna last. Last / remain - to stay inside the sauna I will not last another winter. Tom will remain in Canada until spring. Longest - for the biggest period of time. This is the longest road in the country.

This highlights the competition and the goal Let's have a competition to see who can stay in the sauna the longest Or let's see who can last the longest!

When in the sauna with friends, you want to say something like "Let's have a competition to see who can stay in the sauna the longest". Either of the above comments should fit that scenario. The function of both the example sentences is to challenge someone to do something.

When you are with friends you want to enjoy yourself and have some fun so you might play games/competitions these can also be called 'challenges' you challenge someone to do something Sauna are very hot and some people can't take the heat for too long so you might want to see how long they can last and have a bit of fun as well