The Hebrew letter "ר" is transliterated into the Latin character "r", and it (usually) does not sound like the English "r" (an alveolar approximant), nor like the Spanish "r" (an alveolar tap or a trill), but more like the High German "r" (a uvular fricative). It might take some time getting used to the pronunciation. Luckily though, in case you prefer the English or Spanish "r", some Modern Hebrew speakers do pronounce it that way!
I think you should download a special keyboard which allows you to type nikud. However, I wouldn't recommend doing so. Duolingo doesn't require the use of it, And I think you should concentrate on recognising words without the Nikud and reading&writing more naturally, as it's not so widely used. Mainly in high literature and such.