Hi @Mauricio_Avalos_Martinez 
!
Sorry, it was very very late, here, when I last replied to you, so my last post might have lack some clarity 
!
Manually maintaining the Companies table shouldn’t be required (well, you can if you want to though 
).
All can be done from the Deals table and I mean by that, adding a new/missing company in the Companies table, for example.
How does that work ?
Well, if you take a look at the Lookup field [Companies] in the Deals table, there’s a menu called “Item settings”
In that menu, you’ll find an option to “Allow quick adding of new items”, which I left on ON.
(In this case, the new items will be missing companies from the Companies table)
Meaning that if you add a deal in the Deals table and you can’t find the appropriate company in the [Companies] field you can create that missing company directly from the [Companies] field in Deals .
And just in case this is still not clear, I’ve made a screen recording to show all this “in action” .
In that screen recording, I’m adding a company (which I called Company 8) in the Companies table through the [Companies] lookup field in the Deals table .
Edit : The “long” version of the video can be found here (just in case )