systemfehler
Member
As a rule of thumb: if the "r" is the final letter of a word, it is not pronounced. However, you should keep in mind that this varies regionally and is not a 100% accurate.
edit: Also, the r in Spanish is an alveopalatal consonant, whereas in German, it is mostly a uvular consonant, so their articulation is very different.
So how do you prounounce "Winter", "Krieger", "Februar" ... you made it sound like that when it is at the end you treat it like a silent "H". The "R" at the back sounds normally less aggressive but I wouldn't say that is not pronounced.