Hi,
Thank you very much for your valuable question and I am very glad to know that you are trying to create a question answer Website.  It is very important website because a lot of people will get Useful information from this website.

And you have select the correct theme for your website. Because this theme is very easy to use and install. And you will all features of a ideal Q&A website (See demo from official website). You can see more details from here.  but I will suggest you to buy this theme from there official website  because you will get support 12 month free support.

You should not download and use free theme because

* You will get many unnecessary script on your theme which is very bad for your website.
* This unnecessary script may damage or hacked your  website.
* You must find some script provided by the author of that website from where you will download.

So I will suggest you that do not download and use free theme if you want to run your website safely.

On the other hand, if you buy theme, you will get this following facilities –

* You will not get any unnecessary script on your theme.
* There is no footer credit
* You will get 12 months support from the wordpress expert theme expert (You can get extra support if you need).
* This thing will be 100% safe for your website because there is no hacking script or unnecessary script on your theme.

I will suggest you to download QAEngine 2.0.14 from Engine theme official website and use safely.

So Download download QAEngine 2.0.14 – Question and Answer WordPress theme 

Thanks again for your question.

Yes, I agree with Mohi Uddin.
QAEngine 2.0.14  WordPress Theme is QUESTION & ANSWER WORDPRESS THEME by which  you can easily BUILD YOUR ONLINE KNOWLEDGE WEBSITE.
It Not only helps you create a Q&A website but also inspires your community to share their knowledge.

It’s Simple Design. Quick Engagement. Inspiring Sharing makes this theme perfect. QAEngine also helps you create a fully functional Q&A WordPress website with a clean design and a user-focused experience.

It’s Simple design and Better community interaction. Users can freely ask questions & receive best answers from experts. Quickly submit Q&A entries Easily post a question following simple steps. Quickly contribute an answer & discuss under each question.
Easily find the answer instantly. Users can filter to see questions in a specific category or tag, and choose the most valuable answers to them by looking at votes and the “best answer” mark.

Cultivate a knowledge sharing culture.
Increase contributor presence on your site, encourage the community to share their knowledge.

Different user badge levels & points
The more contribution a user has on your site, the more points he gets and the higher badge he is rewarded.

Exclusive privileges for experts
Set permissions for voting, leaving comments, editing questions & answers or even approving answers for each point level.

So Create your online community site with QAEngine key features

MONETIZABLE QUESTION PUMP
Make money when user buy premium pump plan

USER BADGES & POINT SYSTEM
Grant recognition to your user contribution with multiple badge and ranking levels

RESPONSIVE DESIGN
Your Q&A site appears beautifully on any device and browser

BEST ANSWER CHECK MARK
Encourage quality answers by letting users pick the best answer to their question

INTUITIVE POLL QUESTION
Have fun creating polls to collect multiple answers from voters

EASY USER INTERACTIONS
Optimizing user interaction with answer, discuss, upvote or downvote activities

See demo from here

Thanks for your questions