Android 4.4.2

Hi all, anyone know how to update above system to 5.0 lollipop or above ?
Have tried check for updates in settings, it tells me I have most up to date available.
Tablet is Lenovo A-7600f A10 new in 2016.Trouble is some newer apps won’t work.
Do I have to root which I think may cause a few problems.
Thanks in advance for any suggestions

You can, but it's non-trivial.

Hardware devices have a specific chipset. The operating system needs to be compiled for your specific chipset. The vendor then cryptographically signs the compiled version, so the device trusts the package. Vendors stop doing this for older hardware because there aren't enough users, and to encourage remaining users to upgrade.

So at a high-level, you'll need to:
- Download the latest Android source (easy enough)
- Compile it for your specific device
- Either allow unsigned packages if your device has this option, or jailbreak it if doesn't
- Install your compiled package

If you haven't done this before, good chance you'll end up with a paperweight, so back-up beforehand.