How to use "La" and "El"?
I'm sure a lot of people get confused when it comes to knowing which of these to use in a sentence. I myself am having a hard time understanding the concept of masculine and feminine objects. I know when to put "la" and "el" in a sentence that contains "Nino" or Nina", but I'm not too sure how the rule goes for objects. As I've learned from this site, "some" words that end with 'e' will have "el" before it. Same goes with the letter 'a' and la. But, this site also teaches to put El before "pan" and El before Agua. Can someone please explain to me the concept behind this?
Agua is feminine, but takes "el" as an exception, because of pronunciation, to prevent the clash between the two stressed "a". The same goes for "alma", "arma", "área", "águila", "aula", "arca", "arpa", "hambre", "hacha", "hada"... (Compare "la arena", "la harina"...) However, take care to say "mucha agua/hambre", and not "mucho agua/hambre", since there are not two stressed "a" together.
The rule you describe may help you guess the gender, but there are exceptions. In general not only do you have to learn the meaning of a word but you also have to learn its gender. There is no way around it. With practice, you will remember both, and don't be afraid of making mistakes... we all do.
I find this article quite helpful: https://en.m.wikipedia.org/wiki/Grammatical_gender_in_Spanish
Words with -e are tricky because they aren't predictable, but I guess they are usually feminine. Most words with -a are feminine, including "agua", but words that begin with a stressed a take "el" because "la" comes from Old Spanish "ela" and it became "el" in this case ("ela muger con ela agua" -> "la mujer con el agua").
I found this page very helpful for learning the main rules: https://www.spanishdict.com/guide/masculine-and-feminine-nouns
The rules are not many, but there are exceptions to them. Overall, though, Spanish has a very friendly noun-gender system compared to many other languages. When you know the main rules, you can guess the gender of most nouns correctly. You'll eventually get a good feeling for it too, so that you won't have to think so much about it everytime you want to use a noun.
Finally, mixing up the gender of Spanish nouns usually doesn't matter at all.
And a bit here about the 'el agua' deal: https://www.thoughtco.com/substituting-el-for-la-3079094