Is it necessary to upgrade from macOS 10.7?

Question

macOS

I got a 2011 MacBook Pro 13.3 running MacOS 10.7.
Do I need to upgrade to the latest version 10.10 or some other, and will the laptop slow down after that (i5 2.4GHz processor, 4 GB RAM).
Before that, I didn’t have a deep acquaintance with Macs, so I ask you to forgive me for such questions that are obvious to many.

Answer 1

Update to Yosemite (10.10) it works well on any hardware.

Answer 2

On 10.10 it can slow down in places, 4 gigabytes of RAM is not enough, upgrade to 10.9 - a stable platform with all the necessary patches, 10.10 is still damp.