ZinaAngel55 The person who built the PC could have made a small mistake in mounting the cooler. But separate from that, if you're using generic case fans, even Lian Li fans, they're not going to be nearly as efficient as the fans that came with the AIO cooler. These are specifically engineered to move air over the radiator as efficiently as possible. So please swap back and see whether the temperatures improve enough for your taste.
If that doesn't help (enough), check the cooler mount.
Idle temperatures don't tell you much of anything unless they're obviously too high. When there's a small cooling issue (as opposed to a major one, where you can't run demanding games at all), the idle temps will often be normal, or close enough to not tell the difference.