Module Upgrade

Dear Sirs,

I need your help respecting module upgrade.
I have an exisiting site that was made by external web designer using your template. His subsrciption expired. and yesterday I purchased my onw subscription. Succesfully downloaded needed template.
But when I tried to update extension "Image Show G4" - I met a problem.
When I tried to install new version 1.37 over 1.32 nothing happened. after that I deleted old version 1.32 and installed new updated one Image Show GK4 1.37..
but I immediately found that all my related modules were disappared (made with Image GK4 vers 1.32)
What is wrong? and how can I update Extensions in future? Because in Extension Manager - > Updates I don't see "Image Show GK4" update. What is the right way to update? wihout losing previously done job and modules?
Thanks in advance

after that I deleted old version 1.32

if you removed old version 1.32 it is normal behaviour that all modules related with this extensions are gone. All that you need is to download module, go to extension manager and install. Joomla! will update module if other with the same name exist.

Thanks for advise,
I did exactly that you proposed first time... and after 1-2 minutes of waiting I found that despite of downloading and installing new module... nothing changed. I saw the same 1.32 version. only after that I did a mistake - deleted old 1.32 and installed new 1.37 version and received all my previous work gone.

Please login via FTP and overwrite all files this for sure will update module code to latest version.

Hello, thank you vey much. That is plain and easy. I will do.
Kind regards
Andrey