diff --git a/advanced/learning_bash_scripting.md b/advanced/learning_bash_scripting.md
index 822454d..268c7b8 100644
--- a/advanced/learning_bash_scripting.md
+++ b/advanced/learning_bash_scripting.md
@@ -732,7 +732,6 @@ waldek@debian:~$ which true
 /usr/bin/true
 waldek@debian:~$ which false
 /usr/bin/false
-waldek@debian:~$ man true
 waldek@debian:~$ whatis true
 true (1)             - do nothing, successfully
 waldek@debian:~$ whatis false
@@ -765,6 +764,8 @@ waldek@debian:~$ echo $?
 waldek@debian:~$ test -a does_not_exist
 waldek@debian:~$ echo $?
 1
+waldek@debian:~$ test ! -a does_not_exist; echo $?
+0
 waldek@debian:~$ 
 ```
 
@@ -1108,6 +1109,10 @@ whale says: I'm an animal...
 waldek@debian:~$ 
 ```
 
+## `break` and `continue`
+
+TODO
+
 # Coding challenge - pipe or argument plus action!
 
 Can you expand the previous coding challenge, where you perform a conditional logic on the input of the script and actually *use* the incoming data?
@@ -1118,6 +1123,52 @@ Rename all files from [this](../assets/simple_sort_01.tar.gz) file with an prefi
 Can you give the files that start with an **uppercase** letter a different pre or postfix?
 Can you move the files with lowercase into a different folder?
 
+# Coding challenge - Guess the number
+
+Can you make me a small guessing game like the one below?
+
+```
+waldek@debian:~$ ./test.sh 
+I have a number in mind between 0 and 100
+your quess: 10
+my number is smaller...
+your quess: 5
+my number is bigger...
+your quess: helloworld
+I don't understand you...
+your quess: 6
+disco! I had 6 in mind...
+waldek@debian:~$ 
+``` 
+
+<details>
+
+<summary>Spoiler warning!</summary>
+
+```bash
+#!/bin/bash
+
+difficulty=100
+computernumber=$(( "$RANDOM % $difficulty"))
+echo "I have a number in mind between 0 and $difficulty"
+
+while true; do
+        read -p "your quess: " usernumber
+        if [ $usernumber -lt $computernumber ] 2> /dev/null; then
+                echo "my number is bigger..."
+        elif [ $usernumber -gt $computernumber ] 2> /dev/null; then
+                echo "my number is smaller..."
+        elif [ $usernumber -eq $computernumber ] 2> /dev/null; then
+                echo "disco! I had $computernumber in mind..."
+                break
+        else
+                echo "I don't understand you..."
+        fi
+done
+```
+
+</details>
+
 # Functions - Reuse code to make life easier.
 
 ## defining a function
@@ -1133,10 +1184,15 @@ Can you move the files with lowercase into a different folder?
 # User Interface - Make your scripts user friendly.
 
 * `case` for command line arguments
+* `select` for small menu's
 * [dialog tutorial](https://www.linuxjournal.com/article/2807)
 * [better dialog tutorial](https://linuxcommand.org/lc3_adv_dialog.php)
 * [Ryan's tutorials](https://ryanstutorials.net/bash-scripting-tutorial/bash-user-interfaces.php)
 
+# Arrays in `bash`
+
+TODO
+
 ## Python
 
 [This](https://gitea.86thumbs.net/waldek/python_course_doc) repository has a twenty day course to learn python written by me.
diff --git a/advanced/learning_shells.md b/advanced/learning_shells.md
index 83ad6c3..ef5c416 100644
--- a/advanced/learning_shells.md
+++ b/advanced/learning_shells.md
@@ -26,6 +26,7 @@ TODO
 
 TODO
 
+
 # Shell completion
 
 TODO
@@ -42,3 +43,6 @@ TODO
 
 TODO
 
+# `xxh`
+
+TODO