Corrected capitalization, corrected to American spellings and typos (#30685)

* Translate challenge subtitles and example challenge text to Spanish

* Corrected errors in syntax and punctuation

* Multiple corrections of it/s to its plus other grammar corrections

* Correction and added paragraph to CSS Flex article

* Corrected my own typo

* Corrected capitalization, American spellings and typos

guide/english/working-in-tech/dunning-kruger-effect/index.md

@@ -9,7 +9,6 @@ In the field of psychology, the **Dunning–Kruger** effect is a cognitive bias
 
 ### Why does it matter in Software Development?
 
-
 The DK effect is important to understand for software developers. It can be observed among developers of all ages. This is more prominent among beginners and intermediate level developers. After the initial struggle, they might get overconfident about a language or their designs. This leads them to underestimate the complexity of system requirements or, worse, hampers them coming up with better software designs. For more experienced developers, they seem to have gained wisdom over the years. They are more humble and better at judging the system complexity. (This might not be true to all senior developers though.)
 
 ### Beware!
@@ -18,7 +17,7 @@ DK Effect is exactly opposite of [Imposter Syndrome](https://en.wikipedia.org/wi
 ### How to check if I suffer from DK effect?
 *You can't!* 
 
-Sorry, but there isn't a straight answer to this question. You can ask following questions to yourself:
+Sorry, but there isn't a straight answer to this question. You can ask yourself the following questions:
 
  -  Are you able to give accurate estimates?
  -  Are you open to learning new concepts?
@@ -27,5 +26,5 @@ Sorry, but there isn't a straight answer to this question. You can ask following
  -  Are you able to take criticism and objectively evaluate feedback?
  -  Are you a good listener?
 
- Readings:
+ Further Reading:
  - [Wikipedia](https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect)