If the situation calls for it, you may have to count and spell the numbers in German. It is not a skill that you have to develop, but if you want to learn German, you have to know how to count all the numbers in German.
Steps

Step 1. Learn the numbers:
- 0 - null - noll
- 1 - eins - ains
- 2 - zwei - tsvai
- 3 - drei - drai
- 4 - Fri - legit
- 5 - fünf - fiunf
- 6 - sechs - zexs
- 7 - sieben - siiben
- 8 - acht - ajt
- 9 - neun - noin
- 10 - zehn - tseen
- 11 - elf - elf
- 12 - zwölf - tsvolf
- 13 - dreizehn - drai-tseen
- 14 - vierzehn - legit-tseen
- 15 - fünfzehn - fiunf-tseen
- 16 - sechzehn - zex- tseen
- 17 - siebzehn - siib- tseen
- 18 - achtzehn - ajt- tseen
- 19 - neunzehn - noin- tseen
- 20 - zwanzig - tsvan-tsig
- 30 - dreiβig - drei-sig
- 40 - vierzig - legit-tsig
- 50 - fünfzig - fiunf-tsig
- 60 - sechzig - zex- tsig
- 70 - siebzig - siib-tsig
- 80 - achtzig - ajt-tsig
- 90 - neunzig - noin-tsig
- 100 - hundert - hun-dert
-
200 - zweihundert - tsvei-hun-dert
Etc etc

Step 2. Next, memorize the spelling and pronunciation

Step 3. After that, you should know how to write the "between numbers", such as:
- 21 - einundzwanzig - ain-und-tsvantsig
- 22 - zweiundzwanzig - tsvai- und-tsvantsig
-
23 - dreiundzwanzig - drai-und-tsvantsig
-
Etc etc.
Einsundzwanzig literally translates to "one and twenty". The idea is that you do this with any of the "between numbers" such as:
-
- 36 - sechsunddreiβig - zexs-und-drai-sig
- 44 - vierundvierzig - legit-und-legit-tsig
-
59 - neunundfünfzig - noin-und-fiunf-tsig
Etc etc
Advice
- The "z" in German is pronounced like a "ts" in Spanish.
- The "s" in German is pronounced like a "z" in English.
- In German, "ig" at the end of the word is pronounced like a very soft "k".
- Find a German teacher to teach you a little more about this language.
- The "v" in German is pronounced like an "f" in Spanish.
- The esset (β) sounds like an "ss" in Spanish.
- The "1" (one) is written with an accent, making it look like a "7".
- Find a study group and practice the pronunciation and spelling of the numbers.
- The "w" in German is pronounced like a "v" in Spanish.
Warnings
- Don't mispronounce a number to a native German. You will leave a bad impression on him.
- Do not stress! It takes some time to learn all those numbers.