トイレに行きたいので数分離席してもいいですか？って英語でなんて言うの？

1) Can I excuse myself for few minutes to use the bathroom?
「トイレに行くのに数分席を外してもいいですか？」
excuse で「退出を許す・席を外すのを許す」

こちらは教室などの部屋から実際出てトイレに行く場合。
2) Do you mind if I slip out for few minutes to go to the bathroom?
「トイレに行くのにちょっと席を外しても良いですか？」
slip out は「こっそり抜け出す」という意味ですが、「さっと行ってくる」というニュアンスもあり、またトレイは堂々と行くものでもないのでこの言い方ができます。

ご参考になれば幸いです！

If you were in the middle of an online English lesson, and you need to go to the restroom, and you would like to be asked to excuse yourself to do this, you could say either of the following: "May I excuse myself for a few minutes to use the restroom?" or "Sorry, I just need to quickly go to the restroom. I will be back as quickly as possible".

Examples:

I really need to go to the toilet now, do you mind if I go for a few minutes?

I need to use the rest room, may I excuse myself for a few minutes?

Excuse me Teacher, is it okay if I go to the toilet for a few minutes?

If you are going to interrupt the lesson because you have to answer the call of nature, it is good manners to politely ask your teacher to 'excuse you' briefly to visit the "gents'/ladies' room". So, instead of you saying that you want to visit the 'toilet', you may vary this by calling it the "gents'/ladies' room" depending on your gender. To make sure that the teacher doesn't get the impression that you may be in the gent'/ladies' room for a long time, you may add that you'll be 'back in a jiffy' which means, 'you'll be back ASAP', or, 'in a very short time'. The abbreviation 'ASAP' stands for 'as soon as possible'.
So, you may say:
Please excuse me, I just need to briefly visit the gents'/ladies' room. I'll be back in a jiffy.
or
Will you please allow me to visit the gents'/ladies' room briefly? I will be back ASAP.

When we say "run to the bathroom" we are indicating that it will only take a moment or that we will return shortly.

"I will be back in a moment" - It's a simple way to say please wait, this won't take long.

"I'll be right back" is another way to indicate that the tutor won't have to wait long.

A polite way to interrupt a conversation or lesson is by saying "pardon me." Afterward, one can say what he/she needs to say.

Oftentimes, one may feel that giving the reason for needing to exit the activity for a brief period is too personal, and in that case, it's not always essential to give the reason. One can simply indicate that the reason is unavoidable by stating that it is a pressing matter.

All of these examples politely let your tutor know that you briefly need to excuse yourself to use the bathroom. As well as bathroom you could also say restroom or toilet.

Here are three different phrases that you can use when asking for permission to use the bathroom during a lesson. Notice that the key difference is at the beginning of the sentence with, "do you mind," "May I use," or, "would it bother you."

You want to excuse yourself while you go to the bathroom for a moment. Well, in the UK, it is not necessary to exactly state why you need to leave the lesson momentarily. Just to excuse yourself as in the above examples is quite sufficient. Logic will fill in the gaps. Your teacher will assume that is what you are doing..but in any event, the reason for your absence does not need to be explained.

Could I go to the bathroom really quick?
Do you mind if I go to the bathroom quickly?
Is it okay for you if I go use the toilet for a minute?

When you are in the middle of a lesson but you need to use the toilet and you want to excuse yourself from the lesson, you can use one of these three questions.

I hope that helps.
Have a great day.
Will