Hi @FilippoB and welcome to the Manjaro community.
Perhaps this is something you should not be doing if you are:
…but, at least you’ll have first-hand exposure to problems before most everyone else. 
There is no comparison between Linux and Windows.
I’ve seen several issues raised on this topic. Your system seems capable enough, however, when it comes to Games, it can be difficult to gain the performance you might expect on Linux.
If these are Steam games, I saw one mention of changing to another server (via Steam) that apparently made some difference. If you are trying to run these games via WINE, or another WINE-based method, I doubt general performance will ever improve.
A little housekeeping…
As a new user, please take some time to familiarise yourself with Forum requirements; in particular, the many ways to use the forum to your benefit. To that end, some or all these links will be invaluable:
- [How to] Request Support
- [How to] Find Error Logs
- [How to] Find System Information
[How to] Post Screenshots and Links- [How to] Post Command Output and File Content as Formatted Text
- The Tutorials category, generally
- Forum Rules
- Strict Forum Rules and Guidelines
And last, but not least, the Stable Update Announcements, which you should check frequently for important update related information. Occasionally an issue might be directly related to a particular update; it’s always best to check those announcements.
Cheers.