should I upgrade from safari to Catalina ?

High Sierra to Catalina is quite a jump. At best it will entail a learning curve.

No one can possibly make that decision for you. Read Upgrading macOS without fear - Apple Community. That's what I do.

It depends on how you use your Mac. Mainly, do you have 32 bit apps installed? Catalina is 64 bit only and it's impossible to run such older software on it. This is a very short list of apps that cannot be used in Catalina. I mention these two in particular because they're the ones users ask about most often.

Office 2011 or older

Adobe CS6 and older

Otherwise, Catalina is quite a leap in security. The entire System folder is read only while booted to that volume. So it's literally impossible for any malware to add anything to, remove or modify in that folder. Your own user account is still yours to do with as you please, so it's still entirely possible to install malware/adware into your own account. But no matter what you install, it cannot dig its way into the system.

Safari is kind of different because it comes with the OS. Meaning, it's only going to get security updates, and updates to new web standards for a few years. To get a newer version of Safari, you have to install a newer version of macOS than you currently have. Typically, Apple keeps updates going for the latest OS and at least two versions back. That puts High Sierra at the verge of being cut off from any more updates as Big Sur will be released sometime this fall. But that's based only on what Apple has done the past 6 years or so. Doesn't mean their update coverage won't change to extend further back.

Everyone's a newbie at some time. I'm way past that and still learning.

Safari is a web browser. Catalina is an entire OS.

Since you posted in the High Sierra forum, do you mean from High Sierra to Catalina?