My native language is Croatian and I have been listening to A. J. Hoge who is a teacher from San Francisco. What I hear when he says "not enough" is "norinaf". How would one pronounce it?
There are a lot of examples, one of which is "lot of" (and I hear "loRav"). I'm speaking about American English, more precisely San Franciso, East Coast, where A.J. is living. Another teacher named Rachel mentioned it in a youtube-video.
Some accents would use a glottal stop for t in this context, but if you are listening to an American speaker, and you are hearing something that sounds to your like an "R" sound, it is more likely that the sound is a voiced alveolar flap (or tap), transcribed in IPA as [ɾ].
In most varieties of American English, the voiced flap/tap sound can be used for t within a word when the t comes after a vowel or after r, and before an unstressed vowel (as in butter, letter, reporter). It is used for t at the end of a word when it comes after a vowel or after r, and before a vowel at the start of the next word (stressed or unstressed).
This depends on local dialect and accents, but in Received Pronunciation it would be pronounced just as it looks, as two separate words, not slurred together. I apologize that I neither know the IPA nor how to type it on a standard UK keyboard, but in RP it sounds like "not enuf"
The sound you are hearing is probably a "glottal stop". Some languages treat the glottal stop as just another consonant like p, t, or k, but many (most?) native English speakers use it without even knowing of its existence.
Your question mentions that your native language is Croatian. I don't know much about that language, but Wikipedia's article on Serbo-Croatian phonology might help you to identify the sound:
Glottal stop [ʔ] may be inserted between vowels across word boundary, as in i onda [iː ʔônda].
English speakers often pronounce /t/ as a glottal stop [ʔ] when it appears in certain positions. This is called "t-glottalisation", and it is more common in some dialects than others.
In English phonology, t-glottalization or t-glottaling is a sound change in certain English dialects and accents that causes the phoneme /t/ to be pronounced as the glottal stop [ʔ] in certain positions. It is never universal, especially in careful speech[.]
The t in "not enough" could easily be pronounced as a glottal stop.
