diff --git a/doc/3_advanced.md b/doc/3_advanced.md
index 7507f49..ef1e8db 100644
--- a/doc/3_advanced.md
+++ b/doc/3_advanced.md
@@ -106,7 +106,7 @@ echo -e "Your Message: ${test}\nbye!"
 #### message formatting and keyboards
 
 The output of the script will be processed by 'send_messages', so you can not only send text, but also keyboards, files, locations and more.
-Each newline in the output will start an new message to the userr. To have line breaks in your message you must insert ' mynewlinestartshere ' or '\n' instead.
+Each newline in the output will start an new message to the user. To have line breaks in your message you must insert ' mynewlinestartshere ' or '\n' instead.
 
 To open up a keyboard in an interactive script, print out the keyboard layout in the following way:
 ```bash
@@ -114,8 +114,11 @@ echo "Text that will appear in chat? mykeyboardstartshere [ \"Yep, sure\" , \"No
 ```
 Same goes for files:
 ```bash
-echo "Text that will appear in chat? myfilelocationstartshere /home/user/doge.jpg"
+echo "Text that will appear in chat? myfilelocationstartshere /home/user/dog.jpg"
 ```
+*Note*: Use an _absolute path name_ (starting with `/`), a relative path name is relative to `data-bot-bash/upload`!
+See [send_file documentation](6_reference.md#send_file) for more information.
+	
 And buttons:
 ```bash
 echo "Text that will appear in chat. mybtextstartshere Click me myburlstartshere https://dealz.rrr.de"
@@ -299,5 +302,5 @@ Note: If you disable automatic retry, se above, you disable also connection prob
 #### [Prev Getting started](2_usage.md)
 #### [Next Expert Use](4_expert.md)
 
-#### $$VERSION$$ v1.20-0-g2ab00a2
+#### $$VERSION$$ v1.21-dev-2-gde31231
 
diff --git a/doc/6_reference.md b/doc/6_reference.md
index c453f1d..ff8b502 100644
--- a/doc/6_reference.md
+++ b/doc/6_reference.md
@@ -114,20 +114,30 @@ The main use case for send_message is to process the output of interactive chats
 
 
 ##### send_file
-send_file allows you to send different type's of files, e.g. photos, stickers, audio, media, etc. [see more](https://core.telegram.org/bots/api#sending-files)
+send_file allows can send different type's of files, e.g. photos, stickers, audio, media, etc.
+[see Telegram API documentation](https://core.telegram.org/bots/api#sending-files).
 
-- file names must not contain ".."
-- file names must not start with "."
-- file names not starting with "/" are relative to $TMPDIR, e.g. ./data-bot-bash
-- absolute filenames must match $FILE_REGEX
-- FILE_REGEX is a regular expression, not shell globbing, test you rexexes: http://www.softlion.com/webTools/RegExpTest/
+It's recommended to use __absolute path names__ (_starting with `/`_), as relative path names are threated as __relative to UPLOADDIR__ `data-bot-bash/upload`!
+
+For security reasons the following restrictions apply:
+
+- absolute path name must match the __shell regex__ `FILE_REGEX` (_not file glob_)
+- path must not start with `./` and not contain `../`
 
 *usage:* send_file "${CHAT[ID]}" "file" "caption"
 
 *example:*
 ```bash
-send_file "${CHAT[ID]}" "/home/user/doge.jpg" "Lool"
-send_file "${CHAT[ID]}" "https://www.domain,com/something.gif" "Something"
+# recommended: absolute path
+send_file "${CHAT[ID]}" "/home/user/dog.jpg" "My Dog"
+
+# relative to UPLOADDIR: data-bot-bash/upload/dog.jpg
+send_file "${CHAT[ID]}" "dog.jpg" "My Dog"
+
+# change to personal upload dir
+UPLOADDIR="/home/user/myuploaddir"
+# relative to personal upload dir: /home/user/myuploaddir/dog.jpg
+send_file "${CHAT[ID]}" "dog.jpg" "My Dog"
 ```
 
 ##### send_album
@@ -1145,5 +1155,5 @@ The name of your bot is available as bash variable "$ME", there is no need to ca
 #### [Prev Best Practice](5_practice.md)
 #### [Next Notes for Developers](7_develop.md)
 
-#### $$VERSION$$ v1.20-0-g2ab00a2
+#### $$VERSION$$ v1.21-dev-3-g79402ec
 
diff --git a/doc/7_develop.md b/doc/7_develop.md
index 8439441..9352b47 100644
--- a/doc/7_develop.md
+++ b/doc/7_develop.md
@@ -180,22 +180,24 @@ You don't need all these files after you're finished with your cool new bot.
 
 Let's create a stripped down version:
 
-- delete all modules you do not need from 'modules', e.g. 'modules/inline.sh' if you don't use inline queries
-- delete not needed standard commands and messages from 'commands.sh'
-- delete not needed commands and functions from 'mycommands.sh'
-- run ```dev/make-standalone.sh``` to create a a stripped down version of your bo
+- delete all modules you do not need from `modules`, e.g. `modules/inline.sh` if you don't use inline queries
+- delete not needed standard commands and messages from `commands.sh`
+- delete not needed commands and functions from `mycommands.sh`
+- run `dev/make-standalone.sh` to create a a stripped down version of your bot
 
 Now have a look at the directory 'standalone', here you find the files 'bashbot.sh' and 'commands.sh' containing everything to run your bot.
 [Download make-standalone.sh](https://github.com/topkecleon/telegram-bot-bash/blob/master/dev/make-standalone.sh) from github.
 
 ### Setup your develop environment
 
-1. install the commands git, [shellcheck](5_practice.md#Test-your-Bot-with-shellcheck), bc, pandoc, bc, codespell
+1. install the commands git [shellcheck](5_practice.md#Test-your-Bot-with-shellcheck) bc pandoc zip codespell
 2. setup your [environment for UTF-8](4_expert.md#Setting-up-your-Environment)
-3. clone your bashbot fork to a new directory ```git clone https://github.com/<YOURNAME>/telegram-bot-bash.git```, replace ```<YOURNAME>``` with your username on github
-4. create and change to your develop branch ```git checkout -b <YOURBRANCH>```, replace ```<YOURBRANCH>``` with the name you want to name it, e.g. 'develop'
-5. give your (dev) fork a new version tag: ```git tag vx.xx```(optional) 
-6. setup github hooks by running ```dev/install-hooks.sh``` (optional)
+3. clone your bashbot fork to a new directory `git clone https://github.com/<YOURNAME>/telegram-bot-bash.git`, replace `<YOURNAME>` with your username on github
+4. create and change to your develop branch `git checkout -b develop`
+5. give your (dev) fork a new version tag: `git tag v1.xx`
+6. setup github hooks by running `dev/install-hooks.sh`
+
+Note for Debian: Debian Buster has an old shellcheck version, pls update from [buster-backports](https://backports.debian.org/Instructions/)
 
 #### Test, Add, Push changes
 A typical bashbot develop loop looks as follow:
@@ -349,5 +351,5 @@ fi
 
 #### [Prev Function Reference](6_reference.md)
 
-#### $$VERSION$$ v1.20-0-g2ab00a2
+#### $$VERSION$$ v1.20-3-g232a16b