Hi Petit Lion,
<I>The one sound which I sometimes mess up on is the ü sound.</I>
Funny, those English and Scottish people I used to know (or still know) who were trying to pronounce German had more problems with ö (though of course they also couldn't get the ü right).
OK, here comes my explanation for <I>that</I>:
In English, very often they use the same word to mean different things. <i>that</i> is one of them.
You can use it in a causal (not sure if it's called that) clause: I know <b>that</b> I am stupid...
You can use it in a relative clause: I know the book <b>that</b> is fascinating you.
Notice how in the first one, this word, <i>that</i>, refers to a verb - <i>know</i>.
In the second one it refers to a noun, <i>the book</i>. If this noun actually denotes a person, you use "who" instead of "that" in English, however that doesn't make a difference in German.
It's the first one where in German you use <i>dass</i>, and in the second one you use <i>der, die, etc.</I>, depending on the gender/case, or alternatively <i>welcher, welche, welches, etc.</i> (As for <i>jener</i>, this is different! See below.)
Ich weiß, <b>dass</b> ich dumm bin.
Ich kenne das Buch, <b>das</b> dich fasziniert. (or: ..., <b>welches</b> dich fasziniert.)
There is a special kind of clause in English (again, don't know what it's called, I think it's called gerund) that cannot be directly translated into German. It is then often replaced by either a causal (?) or a relative clause.
<i>I know the boy singing in the choir.</i> Make a relative clause: <i>I know the boy <b>who</b> is singing in the coir.</i> -> <i>Ich kenne den Jungen, <b>der</b> in dem Chor singt.</I>
<i>I don't mind the boy singing.</i> Make a causal (?) clause: <i>I don't mind that the boy is singing.</i> -> <i>Ich habe nichts dagegen, <b>dass</b> der Junge singt.</i>
(Notice how translating the previous as "Ich habe nichts gegen den Jungen, <b>der</b> singt" doesn't quite mean the same thing! It would mean "I don't mind the boy who's singing". See the difference?)
Now for <i>jener</i>: This is <i>that</i> as the opposite of <i>this</i>.
I love this book. -> Ich liebe dieses Buch.
I love that book. -> Ich liebe jenes Buch.
However, better not use this too often. It is actually a lot less common than <i>that</i> in English. In common language it is in fact replaced by the simple definite article: Ich liebe das Buch.
As for the German "ch" sound... All the English and Scottish people I've heard trying ended up saying "k" -- for either of the two "ch" sounds. I agree that for the sharp one (the one in <i>Dach</i>) "k" is probably the closest English sound you can get - however, it still sounds really stupid. The other one (the one in <i>ich</i>), is nearer to "sh". At least I think so, and after all in one regional German dialect (Rheinisch), they actually pronounce that soft ch more like sh (German sch). If you ever listened to a song by the German pop group "Die Prinzen", you'll notice that. Their "main singer" speaks Rheinisch.
For similarly unidentifiable (to me, at least) reasons German novices trying to speak English tend to replace the "th" sound (which we don't have) by a soft s (like the one in Sonne). Again, I personally think there are sounds which are a lot closer - like the d (in some South American dialects, they actually pronounce it like that, don't they?) or the English v (like in value) or the German w (like in Wort).
Now, without wanting to be patronizing, Petit Lion, but how do you judge your own pronunciation? Do you have native German speakers there to ask, or recordings to compare yourself to? (If you are using cassette tapes in class, make sure what you're hearing really <b>is</b> native German!) I have heard English people who claimed they were teaching German but had a horrible pronunciation, and German people who are teaching English but have a horrible pronunciation. Chances are your teacher isn't any good at it either. Also, seeing how much English people struggle with German pronunciation when they <b>do</b> have a German speaker to compare themselves to (that's me), it strikes me they'd believe their pronunciation to be good unless a native would tell them otherwise.
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