Well, that is true if you know the etymology of the words you are using. If they are plain germanic words, then it is easy. If they are based on foreign words, which is true for quite a couple of words, it gets complicated. Germans tend to transfer not only the word but even the pronouncation and sometimes the grammar of foreign words into their own. Don’t try to use one of the several ways of plural possible in german for Cappuccino, use the italian one. It takes a few hundred years to use german spelling for some foreign words (like for the last reformation of the german orthography, which did this for some but not all words, which is still not widely used and which took place nearly a hundred years after the last reformation).
I am a german native speaker and I think it is quite a hard language to learn and to teach.
There are so much rules, subtleties and exceptions to rules… in fact, for a typical rule there are more exceptions than cases following the rule. There is one big mistake you can make when using german: building analogies. It doesn’t work! It may look logical, it may look like the same word with the same stem - but in most of the cases it just doesn’t work.
And for the same pronouncation: There are at least four different ways to pronounce an “e”. That is if the word is plain germanic and not a foreign word…
So, my advice: Don’t try to talk perfect by learning. Try to get 80% right, try to be able to passivly understand certain constructs and then use it to get better.
An example for a hard to get construct are particle verbs, verbs that consist of several parts that are torn apart when using pushed in parts of sentences.
“Leutnant Klinke fiel bei der Schlacht bei den Dueppeler Schanzen, in der die preussischen Truppen Daenemark im deutsch-daenischen Krieg endgueltig schlugen, nachdem sie vorher einige Monate Krieg fuehrten, was im Endeffekt zur deutschen Einigung und der Gruendung des deutschen Kaiserreichs fuehrte|, eine neue Methode der Reinigung der Zuendnadeln der Gewehre ein.”
(The content of this sentence is quite made up).
The verb is “einfallen”. It is torn apart to “fiel…ein”. “fiel” int the context of a battle means “killed in a battle”. So up to the | you think that Leutnant Klinke was killed in the battle. Only then you get a clue that something totally different may go on. With the last word you see that the verb is “einfallen” which means “having an idea”. Well…