Here is a simple table that shows the German spelling of a number, followed by a phonetic pronunciation of the number. Be sure to check out the bottom of the article for pronunciation tips.

English	German	Pronunciation
one	eins	(EYNS)
two	zwei	(TSVY)
three	drei	(DRY)
four	vier	(FEAR)
five	fünf	(FUENF)
six	sechs	(ZEKS)
seven	sieben	(ZEEBEN)
eight	acht	(AKT)
nine	neun	(NOIN)
ten	zehn	(TSEHN)
eleven	elf	(ELF)
twelve	zwölf	(TSVOLF)
thirteen	dreizehn	(DRYZAYNN)
fourteen	vierzehn	(VEERTZAYNN)
fifteen	fünfzehn	(FUENFZAYNN)
sixteen	sechzehn	(ZEKSZAYNN)
seventeen	siebzehn	(SEEBZAYNN)
eighteen	achtzehn	(AHHCTZAYNN)
nineteen	neunzehn	(NOINZAYNN)
twenty	zwanzig	(ZVANSIG)

The TS sounds are sharp like in "tsk, tsk" without the k.

The R sounds roll like the rrr's in GRRR.

The umlaut (ü) is probably the most difficult since there is no sound like that in English. Try to speak "oo" and "ee" at the same time (that means go from "oo" to "ee" and stop halfways), then you get the right tune. In the list above, it is written as "UE". If you speak French: The German (ü) sounds like the French "u" in words like "une", "etude", oder "impromptu".

The CH in Acht is the sound of hawking a loogey.

Say the first "I" in the pronunciation of "Zwei" quickly.

Say "w" like "v".

"E" sounds like "I".

Most Germans do no pronounce the word "fünf" (FUENF) or "fünfzehn" (FUENFZAYN) correctly. As it is much simpler, the often say FUEMF or FUEMFZAYN instead. You need not at all be embarrassed if you do the same.