Thank you
My grandpa's Mac is about that old and not even Google Chrome runs properly on it. I don't think Fortnite will run on it then.
MacOS High Sierra or later
Intel Core i3 2.4 GHz or better
4 GB of RAM or more
Intel Iris Pro 5200 or better
Mac should support Metal: More information https://support.apple.com/...e/HT205073
How to install Fortnite on Mac
First open the "Epic Games" website (https://www.epicgames.com/fortnite/de/download) in your web browser. The download should start automatically. Otherwise, click on the Mac icon. Then open the downloaded file and move the Epic Games Launcher to your "Programs" folder.
Then open the application and log in with your Epic Games account or create a new one. This is used on all platforms to synchronize your progress. Fortnite should appear as the home page. If not, click on "Start" on the left and then select Fortnite under "Play for free" on the right. Now click on "Install".