Hey @ZiRo!,
Here is my written explanation, in case you’d like to go back to it in the future. 
Other tutors might also have something to add.
If I remember correctly, your question was, “When do I use ‘go’ and ‘going’ in a sentence/ question?”
Firstly, both of the following questions and responses are correct and essentially mean the same thing. However, grammatically they are different.
- Will you go on vacation?
Yes, I will go on vacation. - Are you going on vacation? Yes, I am going on vacation.
We use ‘go’ (present tense/ simple present tense of ‘to go’) to indicate something happening in the present. However, as we know will indicates something that will happen in the future. Will go is the future tense of to go. In this sentence, the person is asking if someone is going to go on vacation in the near future.
In the second sentence ‘going’ (present continuous/ present progressive tense) indicates that an action is happening and will continue into the near future.
(* The same explanation goes for both of the answers.)
I have added some websites below if you’d like to read further into the grammar.
If you have any further questions, feel free to write them here or ask me in our next Live Lesson
Hope this helps!
*provides a table with the conjugations of ‘to go’ in all tenses.
*different ways to use ‘going’ and other ‘-ing’ form words