Some questions about Kanji
I just wonder how many kanji one can put into a single word, like just recently I stumbled upon a 3 kanji word like airplane "飛行機" And is it possible to get confused when we encounter several words written all in Kanji next to each other. Is there a way to determine which kanji belongs to each word, since the kanjis are connected to form single words at times. For example if we exclude the last kanji of airplane we get the kanji for "aviation" and if the next word starts for example with this "機" kanji, how do we know if that kanji doesn't belong to the "aviation" kanji to form the kanji for "airplane" ? My guess would be context, but it does get confusing at times.
I'm still a learner myself, but the following is to the best of my knowledge: I don't remember seeing a "single" word written with more than three kanji.
There are composita like 「電話番号」 (phone number), made from 「電話」 (phone) and 「番号」 (number). Another example is 「学校図書館」 (school library), made from 「学校」 (school) and 「図書館」 (library).
Then there are Yojijukugo. Those are composite idioms written with four kanji, for example 「一期一会」 ("once in a lifetime meeting") or 「電光石火」 ("as fast as lightning").
But other than such special cases, I'd say three kanji is the maximum. You also have kana to help you grasp the structure, like particles or okurigana. In general the concept of a "word" doesn't seem to hold as much importance in Japanese as it does for example in western languages.
(If anybody with a better understanding of Japanese than me has something to correct or add, please feel free :) )
I used the term "single" words in contrast to composita that are built of other words. As I mentioned above, 「電話番号」 would be a compositum because it's built from the words 「電話」 and 「番号」. As far as I can tell, your three examples are composita in that sense. With composita, you can probably string together words as long as you like. My native language is German, we are quite good at that ;)
I understand what you mean but I'm pretty sure most English speakers would consider that "bookshelf" or "dishwasher" are single words for example.
And if you can indeed construct a lot of compound words that may be understandable, there is a difference between a compound word that is used and recognized commonly and something that is just made up on the spot.
Even to native Japanese people reading words strung together composed only of kanji is confusing. Words/phrases like Fayke's 厚生労働省 will pop up, but I wouldn't worry about extreme examples, like when words are thrust together without particles to separate them. As you come to know kanji, you'll also start to naturally separate words correctly.
The most common examples would be similar to the use English adverbial nouns, e.g. appending 系 to refer to a system, or 者 to refer to a person.