Slovenian (my language) is also a pain in the ass.
A couple noun cases:
I have a car (Slovenian: avto)
I don't have a car/avta.
I gave my car/avtu new tires. (this one sounds strange but I used it for the sake of case illustration)
I destroyed that car/avto.
With my car/avtom.
Also with the varying nouns the adjectives change too:
I have a fast car - Imam hiter avto.
I don't have a fast car - Nimam hitREGA avta.
I gave my fast car new tires - Dal sem mojemu hitREMU avtu nove gume.
You can also notice how the personal pronoun stays the same in English but is changing depending to context in Slovenian: imam/nimam/sem.
Then in English when you go one car, two carS, three carS. You don't differentiate between two or more of something. AFAIK Slovenian is one of only a couple languages on the world that goes 1: me/jaz, 2: us/midva, 3+ us/mi.
With nouns it's a bit trickier: 1 - avto, 2 - avtA and then 3,4 - avtI 5+ - avTOV
Then with genders, for example:
in English you go:
Male/female: I like this car.
In Slovenian:
Male: Rad imam ta avto.
Female: RadA imam ta avto.
As far as genders go most inanimate objects have a random gender assigned to it. Some animals are male, some female. Sometimes you can find a correlation if the word ends with a specific letter.
Mouse/miš in English it's of neutral gender. But in Slovenian it's a she. "That mouse" becomes "Tista miš" tista indicating a female gender. Refrigerator/hladilnik is male "Tisti hladilnik". But the sea for example is neutral gender. It's all mixed up.
Then there's also special characters like Č,Š,Ž. Learning where to put commas was also a pain in the ass in Elementary and is sometimes troublesome even for higher educated individuals.
Honestly, it's hard for me to understand you have educated adults in English speaking countries that have issues with basic grammar and word spelling considering just how elegant and simple to learn your language is. Well I kind of understand the issue with spelling since you don't spell phonetically but still...