注文したデザートを持ってきてもらってもいいですか？って英語でなんて言うの？

The first option is not a question but a statement which will let the waiter/waitress work out what you want them to do. The second is a question which is more specific and tells them exactly what you want them to do. Both of these are acceptable as long as the word please is added somewhere in the sentence so that it is polite.

The waiter/waitress might not always know you are ready for your next course (dessert) so you might have to ask them to bring it to you so you could ask 'could you bring/could I have my dessert now please?' this is a nice polite way of asking him/her

"I would like to order some desert please" is a friendly and polite way to let the waitor know that you are ready to order. "May I please see the desert menu?" is also friendly and polite but more direct

The two sentences you see provided above are great ways to express to your waiter that you now want your dessert. In the second sentence you will see the noun pain. This means trouble or bother. This word would make an excellent addition to your vocabulary since it's a word that is used in both formal and informal settings.

"Excuse me, can you bring out the dessert now?" Once you have finished your main meal, you will want to ask for your dessert. To do so use this phrase. By saying "excuse me" beforehand you will politely gain the waiter/waitresses attention.