When do we use definate articles? Dl we use them all the time?
Not ALL the time, but pretty much all the time
The major exception that comes to mind is when you're using estudiar or aprender you don't often include the definite articles, and you don't often use the definite articles when you use a verb + language, like hablar español/italiano/chino/japonés but you do tend to use it when you're starting a sentence - like el escocés es una lengua "Scottish is a language"
I outline most of what I've come to learn about definite/indefinite articles here
And I think SpanishDict does a good job outlining things too
Spanish Articles - Definite Articles | SpanishDict
In general, you use the articles more than you don't use them. When I don't know, I tend to use the article.
I feel more comfortable omitting them if I'm listing things like a shopping list, or if I'm in an informal setting or texting people