fix(guide): simplify directory structure

guide/english/ruby/ruby-string-operations/index.md

@@ -0,0 +1,47 @@
+---
+title: Ruby String Operations
+---
+Both concatenation and multiplication can be performed on strings.
+
+## Concatenation:
+
+*   Strings can be joined together using any of the following methods:
+    *   `+` operator
+    *   `<<` operator
+    *   `.concat` method
+    ```ruby
+    "Hello" + " World" + "!"  #=> Hello World!
+    ```
+
+    ```ruby
+    "Hello" << " World!" #=> Hello World!
+    ```
+
+    ```ruby
+    string1 = "Hello"
+    string2 = " World!"
+    string1.concat(string2) #=> Hello World!
+    ```
+
+## Multiplication:
+
+*   Strings can be multiplied by an integer value using the `*` operator.
+    ```ruby
+    "Hello" * 3 #=> HelloHelloHello
+    ```
+
+## Replacing a substring
+
+*   We can search for sub-strings or use Regex for searching and replacing character within a string. 
+    ```ruby
+    "Hey mom, look at this string".sub('mom', 'dad') #=> Hey dad, look at this string
+    ```
+
+## Comparison:
+*  Strings can be compared, returns -1, 0, +1 or nil depending on whether string is less than, equal to, or greater than other_string.
+```ruby
+"abcdef" <=> "abcde"     #=> 1
+"abcdef" <=> "abcdef"    #=> 0
+"abcdef" <=> "abcdefg"   #=> -1
+"abcdef" <=> "ABCDEF"    #=> 1
+```