Whilst G2A is legit, it is not problem-free. A lot of people see big YouTubers sponsor them and predict that the website is just as hassle-free and reliable as any shopping site such as Amazon or Steam.
Incorrect. Whilst I continue to use the site because of the cheaper prices, I have had many issues with G2A. Yes, I have always resolved these issues and have eventually got a refund or a working game key but occasionally these problems have taken weeks and on one occasion even a month to resolve.
If you do not need your purchase instantly and you think it is worth the time and effort to email back and forth, provide evidence that you don't own a specific product and wait some time to get what you purchased or a refund for it, then by all means, go ahead and use the site like I do.
Even though I have had bad experiences with G2A, I still use the site as for me, it is worth the possible hassle for a cheaper game key.