Navbar breaking when trying to add a new theme from Bootswatch [ASP.NET MVC5]

I am trying to add a new theme from Bootswatch, but I am just getting familiar with MVC and can't figure out where's the problem.

I read that this is a known issue related with not compatible bootstrap versions. I have read the following:

Adding new Theme to ASP.Net MVC 5 dont work

Bootswatch theme not working correctly

Bootstrap migration

I updated my bootstrap version via NuGet to match the latest version [v5.2.1] of bootstrap in Bootswatch, but the issue still persist.

Any help will be much appreciated.