Problem ws update High Sierra > Mojave

Hi, All.

I have issue with update from High Sierra to Majove.

Currently I have 10.13.6 on MacBoo Pro mid 2012 (much minimum requirements).

When I try to install the update from the AppStore, it shows me this:

I never did download through the Apple Store, and do not know how to delate it and do again.

So i tried to download directly from Apple web site. And once downloaded when I am opening it says that to install Majove 10.14.6 I need 10.14.

Can you please help me?! What is have to be done?

Regards