Some German words are built by combining other words

I learned deutsch (German) today. It is better for me to write it down, so I do not forget.

1)  word + word

There are some words in Germany built by combining other words. For example, the “züruckbezahlen” (pays back) word   consists of two words: “zurück” (back) and “bezahlen” (pay). This word is listed in dictionaries. However, there are some combined words  not listed in dictionaries which could be quite frustrating for a new beginner when he or she can not find the combined word meaning from dictionaries.

There are words which have different meanings when combining it together. For example, the “sitzen bleiben” means to sit on the chair, and “sitzenbleiben” means to repeat the course in the school again.

There is a joke. There are two sentences. Words are the same. They are written a bit differently. They have different meaning. 

- Ich gehe in die Klasse, um dort sitzen zu bleiben. (I go into the class just to sit there.)

- Ich gehe in die Klasse, um dort sitzenzubleiben. (I go into the class to review the learned material again there)

A kid may say that I am going into the class just to sit there, but their parents may though that their child goes into the class to study. 

2) word + one character + word

Sometimes, two words are connected together with a single character. For example, the “Wirtschaftskrise” (Economic crisis) has a character “s” in the middle to connect “Wirtschaft” and “Krise.” The actual meaning is “Krise der Wirtschaft” (Crisis of the econimic). If you understand genitiv, then you would understand the function of the article “der” here which means “of.”  Another example is “Wirtschaftslage” (“Lage der Wirtschaft,” Situation of economic).