Header and Header Top improvements

Problem/Motivation

1. Wrong position of the items of the main menu on mobile screen
2. Wrong position of the dropdown user menu
3. Improve language switcher block
4. Improve navbar-default block

Steps to reproduce

1. Open mobile main menu.
2. Open dropdown of the user menu on mobile screen
3. Check alignment of the language switcher block on the mobile screen.
4. If you use two rows header settings and open search popup we can see the overlapping search form

Proposed resolution

1. Remove align-items style from navbar class.
2. Change the top position for the dropdown of the user menu.
3. Improve alignment of the language switcher block.
4. Improve z-index for the navbar-default block.

Remaining tasks

N/A

User interface changes

1. The items of the main menu have a left position on the mobile screen.
2. The dropdown of the user menu has a correct position.
3. The language switcher block does not have a correct alignment on the mobile screen.
4. The search form after opened does not overlap.

API changes

N/A

Data model changes

N/A