If i update software on my MacBook Pro , AND IF IT UNDATES CATALINA, my computer locks up. Therefore i hhave been advised NOT to update my laptop.

Your computer should not have problems when updating macOS so you should investigate what is causing the update to cause problems. To help us help you look for possible software issues run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper. Can you provide any more details about what happens? Have you made sure all your third party apps & drivers are updated and are compatible with the Catalina update?

Try running the Apple Diagnostics to look for possible hardware issues.

Here is an Apple article showing how you can prevent updates from installing automatically, however, once you resolve the underlying problem you should re-enable the updates. At least leave the new update notifications checked so you know when updates are released.

https://support.apple.com/guide/mac-help/get-macos-updates-mchlpx1065/mac