How to make full width navigation menu?

It’s not full width on the demo site, what do you mean by full width?

Well, that dark blue color behind the nav menu, that goes beyond my red lines, left and right, until the edge of the screen.

Could you link your site?

I don’t have it live yet, I work on localhost. This is how it looks for me:
https://i.imgur.com/bbiJ9S4.jpg

See the difference?

I see your issue now, could you replicate the issue in a sandbox environment and send us a link to that instead?

I actually don’t know what this sandbox is. ?? Sorry, I’m pretty much begginer in this thing.

A sandbox just like a sandbox in real life (for toddlers) but instead for developers. It’s an environment where developers can test out bits of websites and share out the results to everyone.
You don’t have to be a developer to use one.

This is the Sandbox I recommend: https://cssdesk.com

What you need to do is:

1. View any page with the issue,
2. Right click on the page (where applicable)
3. Select the “View source” option.
   A window should popup with lots of code inside.
4. Copy all of that code and go to https://cssdesk.com
5. In the CSSDesk page empty out these sections outlined in red: https://snag.gy/NB1Mw.jpg – Those sections should have no code in
6. Then in this section put that code you copied from the “View source” popup window (step 3): https://snag.gy/sKLG0.jpg

Can you try deactivating all plugins to explore whether any could be responsible?

Can you also try deactivating all plugins on your WordPress site to explore whether any could be responsible?

If you manage to replicate the issue in CSSDesk then you can generate a link to share your sandbox with us: https://snag.gy/u8UlQ.jpg (outlined in red)

I tried but share button doesn’t do anything. Tried in Chrome and Firefox. Maybe this will help:
https://pastebin.com/daFW4DA8

I see how this sandbox isn’t going to work because it’s pointing back (and not finding) to your local files, such as stylesheets. So the sandbox is missing a lot of CSS when I try your PasteBin code.

Can you try to find someone else who has the same issue? It’s tedious but you can look through the Terrifico subforum support topics: https://www.ads-software.com/support/theme/terrifico .

So, your best chance of resolving this issue is providing us with a live example of the issue.

I don’t know why it’s not going full width. The navigation menu was in line with logo in header, but I put it below the logo.

Have you been making much modifications to the theme’s files?

None.

Could you try reinstalling the theme?