I always hear people in videos pronounce the R for example in: car, world, word, argument etc. But in my dictionary these kind of words don't have R written in their pronounciation. So is it ok to not pronounce it? Is there a difference?
Welcome to the forum, Lukas.
Speakers of some varieties of English pronounce the /r/; speakers of other varieties don't. See: Rhotic and non-rhotic accents - Wikipedia, the free encyclopedia