edit function.php and lost my site

Step 1: Redownload functions.php off www.ads-software.com.
Step 2: Use your FTP programme to navigate to your theme folder.
Step 3: Override your messed up functions.php with the one you just redownloaded.
Step 4: Ask Google before you edit functions.php again.

Thanks for your prompt reply. I am newbie here and need more clarification please:

for step 1: May I again download the “Twenty Fourteen theme of version 1.2” or I will reinstall the wordpress 4.0 !

for step 2: give me details of FTP programme procedure to navigate my theme “Twenty Fourteen theme of version 1.2”

for step 3: from where and how will i execute it.

for step 4: I want to change “Howdy admin”. How will i do that

Nope, all you really need is the one file: functions.php. It’s located in the main folder (wp-content/themes/twentyfourteen/functions.php).

There is a guide on using FTP programmes in the WordPress Codex. Find the location of your bad functions.php (same location as above), and override it with the newly downloaded functions.php. The WordPress Codex will tell you how to do that.

In order to replace the “Howdy admin” bit, you can use plain simple plugins. If you only want to get rid of the “Howdy” part, here’s an example plugin: https://www.ads-software.com/plugins/tm-replace-howdy/
There’s plenty more plugins where that came from.

If you ever think there’s something about WordPress you’d like to change: There’s probably already a plugin for it.

Happy customising!

Wao!
At last it is solved and I thanked wordpress team very much.

Please give me some advice to improve my site https://www.kodbel.com

Regards

There’s a WordPress subforum for those kinds of requests.