Double Items Listed In Office

[Şerban S.]

[...] Any suggestions? [...]

A question:
Do you really need both versions?
Because LibreOffice is designed exactly this way: You can install two different versions aside.
My question arises from the fact that I had trouble with the default LibreOffice version which comes with the LL distro and I had to replace it with an older version that actually works.
The trouble I had with the provided version, was that it broke all my tables and I make a heavy use of LibreOffice and have tens of thousands of .odf files in my archive.

If you tested the default installation and works fine, than you can uninstall the "extra" installation, via Synaptic Package Manager.
I do it after every new (clean) Linux Lite Install if I get into trouble so it's a proven solution.
Hope this will help you.
The Menu Editor solution, only removes  the links from the menu, leaving the installation where it is and you'll end up being unable to run one of the LibreOffice's instances.