Get a magazine that is specificly made for the pistol.
Do some checking as the FEG models are confusing. With the discription posted from the auction it's most likely a FEG AP9,,the 32cal version.
Most of these pistols are found in 380cal and so most of the extra magazines are too.
I don't know if there are separate mags for the 2 calibers (it would seem so) or if they use the same one.
Lot's of info, sometimes confusing, on the net about the FEG pistols.
You can try stretching the magazine spring on the one you have.
It can give a little more tension to it and sometimes solve a feeding problem.
Take the follower and spring out of the magazine body. You may have to remove the floor plate to do that,,I'm not familiar with them.
Once you have the spring itself in hand,,gently and carefully pull/stretch it out so it's overall length is perhaps 1 to 2 inches longer than it was when you took it out of the mag. Measure first!
There's sometimes a top and bottom to the spring itself. If the wrong end is pushing on the follower, it can cause feeding problems.
Many of these military/police type Euro pistols are generic when it comes to stuff like that but it's something to look at.
It'll only go in one of two different ways. Try both for functioning if you're not sure.
Check for any kinks in the spring that may be causing the problem. Dents in the mag body can do the same as well.