Hey @lezard1999!
I’m not sure about matching perfectly, (especially those pesky fingers) but there is a built in “Modify Pose” you can use in the “Retarget Sources” tab in your skeleton. From there you would rotate/lower your arms downward 50 degrees, and that would match up with the Epic standard, and select “Use current pose”.
Here is the documentation (follow Manage Retarget Bone base near the bottom which shows how to quickly correct T-Pose bones) and a reference screenshot to show the location of the button you are looking for:
I hope the above solution is what you are looking for!