That will be macOS 10.13.6 High Sierra.
If you are having trouble connecting to and using websites with your older version of Safari, try it with a newer third party browser that is still being updated to meet current internet security protocols.
I suggest you take a look at Firefox browser (the ESR release) or Brave browser.
Download an alternative browser and install it into your Applications folder. Launch and use that when you encounter websites that don't play well with Safari.
Also, consider that your MBP is now thirteen (!) years old. You would be wise to plan for its replacement.