Bootstrap Dropdown disappears only on WP

Hello there,

I’m new in the WP world and my first project needed a custom theme.

I’ve written the whole theme by my self and now I’ve a problem with the bootstrap dropdown menu at the nav-bar.

I’m using the navwalker from GitHub to provide the dynamik WP Nav.
The menu is generated propperly and shows the right way. But the dropdown disappears when it was hoovered. Even when I clik a in the dropdown-list, but the link is working!

What I tried to fix:

• copied the WP generated navigation into a empty HTML-File, there it worked without an issue
• opend the site in different browser’s
• added the following to my CSS

.navigation ul {
 top: 45px;
}

• deactivated my plugins one by one and checked if it worked, was not the problem
• checked the margin values, and even there was nothing found

Actually I can’t provide a Link to the site, it’s still on my computer for developing. Can this be the issue?

Thanks for help