Translation:the letter r
For many years, the only official way to write Klingon is the way Dr Okrand wrote it in The Klingon Dictionary, i.e. with mixed-case Latin letters as in tlhIngan Hol.
Later, various other symbols became used as well, though they were not considered official at first.
One such set, which has a one-to-one correspondence with romanised Klingon letters (e.g. one symbol for tlh, one for ng, etc.), later got used on the Klingon version of Monopoly, and many consider it to be official since then. But it wasn't designed by Dr Okrand.
I'm assuming you heard the male voice - the female voice definitely gives a little roll, but the male voice just does a tap. I'm pretty sure the German r is produced at the back of the mouth (like the English r) and I hear both of the voices doing the Klingon r sound at the front of the mouth. I will link both the male r and the male gh for you to compare.
Those both sound like gh to me, as in ɣ, or the voiced velar fricative. The male version is softer than the female version to be sure. (https://upload.wikimedia.org/wikipedia/commons/4/47/Voiced_velar_fricative.ogg)
Where as the Klingon r should sound like a rolled r, or /r/, a trill. (https://upload.wikimedia.org/wikipedia/commons/c/ce/Alveolar_trill.ogg)
There's disagreement within the Klingon speaking community as to whether the proper sound is a tap or a full trill. Dr. Okrand describes it as a "light trill" and then does a tap himself. I suspect he meant tap, but knew most fans wouldn't know what that meant so he described it as a "light trill" instead.
In practice, Klingon speakers accept the tap and trill in free variation.
I am a skilled Spanish speaker and I clearly hear these r sounds being pronounced at the front of the mouth. I don't know how to "fix" them for you.