In this video, we learn the numbers (and how they are pronounced) from eleven to twenty in German as follows:

eleven - elf
twelve - zwölf
thirteen - dreizehn
fourteen - vierzehn
fifteen - fünfzehn
sixteen - sechzehn
seventeen - siebzehn
eighteen - achtzehn
nineteen - neunzehn
twenty - zwanzig

To practise these words further, please visit:
https://lexicogs.com/basic-german-vocabulary-numbers-eleven-to-twenty/