It is very difficult to explain it. I think we sometimes use these two words interchangeable: Bu benim görüşüm/fikrim, katılmak zorunda değilsiniz." or fikir/görüş ayrılığı, görüş/fikir birliği, aynı görüşte/fikirde ol(ma)mak, but not always. For example you can not say dünya fikri instead of "dünya görüşü". There is a slight difference i think.
It is one of a group of words that loses its second vowel. This only occurs in two syllable words, most of which are of foreign origin, although not all of them are.The vowel that is dropped is almost always a high vowel [i/u/ı/ü] (I can't think of any with low vowels, but I am not 100%).
These just have to be memorized as they come along, and you could find information regarding this in any reputable Turkish dictionary. Some other words that do it are: şehir, omuz, ağız, and beyin