First impressions have a big impact on how others perceive you, so how you introduce yourself to others is extremely important. Many people call an introductory speech an elevator speech, because it should be succinct enough that you could introduce yourself and tell someone about your goals or interests in the time it takes to ride an elevator.  It may also be called an "icebreaker" speech, as it breaks the ice and lets others get to know you.  Consider your words carefully when you write a speech introducing yourself. Crafting a good self-introduction can either build or harm your credibility.
Questions are a good opportunity for you to interact with your audience. It may be helpful for you to try to predict what questions will be asked so that you can prepare your response in advance. You may wish to accept questions at any time during your presentation, or to keep a time for questions after your presentation. Normally, it's your decision, and you should make it clear during the introduction. Be polite with all questioners, even if they ask difficult questions. They are showing interest in what you have to say and they deserve attention. Sometimes you can reformulate a question. Or answer the question with another question. Or even ask for comment from the rest of the audience.