"There isn't going to be much time."
Translation:No va a haber mucho tiempo.
No hay is present tense = There is no(t). No hay mucho tiempo = there is not much time. Hay comes from haber. Duo's sentence asks for going (ir a) and there + to be (infin. haber).
Also accepted is 'No habrá mucho tiempo'. Habrá is the 3rd person future tense conjugation. Technically the sentence `No habrá mucho tiempo' would mean 'there will not be much time'.
The future tense is used for the following:
- to refer to something that will happen at a future time, e.g. Algún día iré a Buenos Aires: One day I will go to Buenos Aires - to make predictions , e.g. Empezarás una nueva vida en otro país: You will begin a new life in another country. Another example, En el futuro los robots harán todo el tabajo: In the future, the robots will do all the work. - to state probabilities, e.g. Este verano probablemente acabaré mis estudios: This summer, I will probably finish my studies.
The phrasal construct ir a + infinitive is used for the following:
- to refer to current plans or intentions in the future, e.g. vamos a casarnos este año: We are going to get married this year.
- to refer to something that, because of present circumstances, seems sure to happen. e.g, ¡Daos prisa! ¡Va a salir el tren!: Hurry up. The train is going to leave.
This particular sentence 'There isn't going to be much time', could fall into either category of a prediction, or to refer to something that is sure to happen because of present circumstances. Hence why I believe that both ir a + infinitive and future tense are correct ways to translate this sentence with no further context.