Some games are developed in a different way and because of that it's possible that Avire treats them as potential malware. However, I recommend you scan these files, but if you know they're safe, then add them to the Exception list.
Luckily, Avira created a page with detailed instructions on how to achieve this. I recommend you visit the following page to learn how to add the games to the Exclusion list to prevent a possible deletion when Avira's scan is in place.
Knowledge base URL: https://www.avira.com/en/support-for-home-knowledgebase-detail/kbid/1257