Student or Learner
1.I hope there won't be many people there at the time.
Is the second "there" necessary?
2. I like pineapple(s). Plural or singular?
1. Yes. Maybe. The second "there" replaces the fuller description of where you are talking about. I hope there won't be many people [at my house / at the bank ] at the time. Without it, we may not know where you don't want the people to be.
However, if it's very clear from the context, you could omit it. You could even say, "I hope there won't be many people" and stop there, if the context was clear about where, and when, you were talking about.