upgrades and customizations

Dear, I’m new in SuiteCRM , I have to upgrade SuiteCRM, how can I keep all my customizations ?
Thank you very much.

You just upgrade and they’re kept, IF (AND ONLY IF) they were upgrade-safe customizations.

Which version are you coming from, and which version are you going to? This is much harder when you’re skipping many versions.

You probably want to get a clone and test the upgrade first, and check all your customizations, before doing it with your live data.