Agreed, French was very difficult to learn.
BTW, did you know that it’s not that the French haven’t invented a word for ninety, even eighty or seventy for that matter but it goes back to the vigesimal or base 20 numeral system which is based on twenty (in the same way in which the decimal numeral system is based on ten)?
70 = soixante-dix = sixty ten .... 80 = quatre-vingt = four twenty .... 90 = quatre-vingt-dix
However, that only applies to French spoken in France!
The French speaking Belgians and Swiss have words for those numbers although they don't both use all and the same, just to keep everyone on their toes, I guess i.e. septante, octante or huitante and nonante.